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About  Thread

For my personal tieing, I use primarily Lagartun ,Wapsi Ultra 70 and 140, and Gudebrod 45 denier polyester and Veevus 30 denier gel spun,  along with Wapsi 130  or Wapsi 75 denier gel spun for deer hair work.  These threads provide the right strength, size, and appropriate attributes such as the ability to flatten that I find makes tieing durable and beautiful flies much easier.


In the summer 2004 issue of Fly Tyer, author Lyle Morgan addressed the question of whether standardizing thread size would help tiers become more effective in producing beautiful and effective flies. It certainly makes sense to have standardization, which would eliminate much of the confusion that surrounds fly tying thread today. Based on the fly tier web poll conducted in the same issue as Lyle’s article, voters overwhelmingly agreed (252 to 32) that thread should be standardized. The process has been almost fully implemented over the  past eight years.   Most thread spools with a few exception put the denier rating on the spool label.  ”Fly Tyer” magazine includes the appropriate denier in all of the fly pattern recipes.  This has been a hugh help in slowly educating their readership on this correct method of measuring thread.

Tom Schmuecker of WAPSI started the denier information process by introducing WAPSI UTC 70 and 140 denier threads in 1998. His purpose in using the denier number rather than the “aught” was to try and subtly suggest that this system was more beneficial to the tier than the “aught” system that had existed for more than seventy years. Denier is also a recognized and accepted standard of measurement among thread manufacturers and the garment industry.  The term “denier” was coined by the French in 1535.  It is not a new term.

A good example of the misuse of the “aught” system is Gordon Griffith 14/0 Sheer thread.  This thread is acutally a 72 denier thread, but the aught rating would suggest it is much smaller than other threads in the 70 denier category.  The use of the 14/0 rating was designed to mislead the unsuspecting fly tier.  Another clue is that the breaking strength when test by Bill Merg was 10 ounces.  I obtained the actual denier rating from a representative of the late Gordon Griffith’s company who contacted the manufacturer for the denier rating on all of the threads that they sold.

Another good example of how confusing the “aught” rating can be is a comparison of Gudebrod’s 10/0 polyester thread, Bennechi’s 10/0 thread.  The denier of Gudebrod 10/0 is 45, and Bennechi 10/0 is 120.  The aught system does not allow an apples to apples comparison.  Using denier does provide a good comparison between threads.

The late Jean Guy Cote’ of UNI Products was already putting the denier on a number of his products in 1995. He stated, however, ” I won’t put the denier on the 8/0 thread until I am sure that all of the other distributors are using the same measurement system to identify the denier of their thread”.  He had already identified in a chart the denier of all of his products. This information is available to anyone requesting it.

Although Gudebrod closed the company in 2006, at the time I interviewed Paul Black of Gudebrod he stated, ” I have already started to put the denier number on the labels of our thread since we do all of our printing in house” Of course, this process may take a year or more to complete given the number of thread sizes (7) and the multitude of colors. These new labels will begin to show up in fly shops gradually as the proprietors order new stock.  Gudebrod thread is still available in some shops even today.  I still have a reasonable selection of sizes and a number of colors.

Danville manager, Dan Bezanson, stated, “Wherever possible, Danville will include the denier on the spool label.” A few labels may not contain the denier due to unavailable space. Danville recently introduced a 140 denier thread that does not have an “aught” designation.

Giorgio Benecchi Products, of Modena, Italy, does not have labels on their spools. However, they do provide this information freely to shops or distributors. In my own shop, I use a rubber stamp to put the denier as well as the “aught” rating on each spool of Benecchi thread.

Historically the “aught” system began in the late 1930’s. Dan Bezanson said, ” Based on the information that has been handed down in the company, Danville Chenille implemented the “aught” system to help standardize fly tying thread. This was based on a system where the number 0 or “aught” was the base point and as the thread became smaller additional zeros were added indicating that the thread was finer. As an example, a thread with six zeros (000000) translated to a 6/0 thread. As other thread distributors came into the market place after the early 1960’s, they followed the same system which was assigning an arbitrary number that does not necessarily provide as accurate a measurement for the fly tier as denier.

As more thread distributors and brands became available, the accuracy of the “aught” became muddied. When only one distributor existed, making some sense of the system was not difficult. Now there are at least seven distributors of thread in what has become a very competitive market. It occurred to me in the mid 1990′s that some of the aught numbers being assigned to some thread was a matter of trying to gain a competitive edge rather than providing accuracy for the fly tying customer. That is precisely what Denier is defined as the weight in grams of 9000 meters of nylon, polyester, rayon thread, etc. There is a correlation between denier and breaking strength of nylon and polyester thread. The smaller the denier numbers the lower pound / ounce breaking strength of the thread. At the present time, about the smallest denier nylon or polyester for fly tying thread is 20, which would be used for tying midges. The one exception to this denier vs. breaking strength rule is that gel spun polyethylene thread is two to three times stronger than nylon or polyester thread of the same denier.

Denier is only one factor the tier should take into consideration when selecting a thread. The type of material of which the thread is constructed should be considered, whether the thread is a continuous filament, simple twist, bonded, or a rope type. Nylon has about 25% stretch, polyester around 15% stretch, and gel spun only 3% stretch. The type of material being used on the fly as well as the appearance desired also has to be considered. It is important to experiment with all of the various threads available to gain a complete understanding of the pros and cons of each.


Listed below are some of the most popular brands and sizes of threads available. Compare the denier of the thread you are using with others of a similar “aught” size.

Thread Brand Aught Size Material Denier Breaking Strength Thickness (.000)
UNI Caenis N/A mono 20 3 oz. 1.7
Veevus 16/0 polyester 50 12 oz.  *
Veevus N/A gel spun 30 1 lb. 7 oz 1.0
Veevus 14/0 polyester 70 14 oz. *
Veevus 12/0 polyester 70 14oz.  *
Gudebrod 10/0 polyester 45 9 oz. 1.0
Euro Thread 12/0 polyester 45 15 oz. 1.3
UNI 17/0 nylon 40 5 oz. 2.0
Danville Spiderweb N/A mono 30 5 oz. 2.0
Roman Moser Power Silk 8/0 gel spun 55 2 lbs. 6 oz. 1.3
WAPSI 50 GSP N/A gel spun 50 2 lbs. 5 oz. 0.8
UNI Cord 12/0 gel spun 50 2 lbs. 7 oz. 0.9
Benecchi Ultra Strong N/A gel spun 50 2 lbs. 6 oz. 1.3
Benecchi Ghost N/A mono 60 11 oz. 3.0
Veevus 10/0 polyester 110 1 lb. 5oz.  *
Gudebrod 10/0 mono 50 2 lbs. 11 oz. 6.0
Gudebrod 8/0 polyester 67 15 oz. 1.8
Benecchi 8/0 polyester 150 1 lb. 13 oz. 2.2
Veevus 8/0 polyester 110 1lb 7 oz.  *
Benecchi 12/0 polyester 70 15 oz. 1.9
Lagartun N/A polyester 74 1 lb. 1.2
Gordon Griffith Shear 14/0 polyester 72 14 oz. 1.8
Montana Fly Co 8/0 nylon 72 14 oz. 1.4
Gudebrod GXI gel spun 70 4 lbs. 4 oz. 1.0
Danville 6/0 nylon 70 11 oz. 1.5
UNI 8/0 polyester 72 15 oz. 2.0
WAPSI UTC 70 N/A nylon 70 13 oz. 1.1
Lagartun N/A polyester 95 1 lb. 1 oz. 1.4
Gordon Griffith Wisp 8/0 polyester 108 15 oz. 2.2
Veevus 6/0 polyester 110  1 lb. 8oz.  *
Montana Fly Co 6/0 nylon 110 1 lb. 7 oz. 2.0
Gudebrod 6/0 polyester 143 1 lb. 15 oz. 2.3
Benecchi 10/0 polyester 120 1 lb. 6 oz. 2.0
Danville Monocord 3/0 nylon 116 1 lb. 10 oz. 2.6
UNI 6/0 nylon 135 1 lb. 13 oz. 2.9
WAPSI UTC 140 N/A nylon 140 2 lbs 12 oz. 1.6
UNI Cord 7/0 gel spun 100 5 lbs. 9 oz. 1.4
WAPSI GSP 100 N/A gel spun 100 6 lbs. 15 oz. 1.2
Gordon Griffith Cobweb 2 N/A polyester 134 4 lbs 3 oz. 4.1
Wapsi N/A gel spun 130 6 lbs. 8 oz. 2.0
Veevus N/A gel spun 150 8lbs. 4oz.  *
Roman Moser Power Silk 6/0 gel spun 110 4 lbs. 8 oz. 1.3
Gudebrod 6/0 mono 143 2 lbs. 11 oz. 6.0
Lagartun N/A polyester 150 2 lbs. 1.9
Danville Flat Waxed Nylon N/A nylon 210 2 lbs. 14 oz. 2.0
Danville Fly Master Plus N/A nylon 210 3 lbs. 2.8
UNI 210 N/A nylon 210 3 lbs. 3 oz. 2.0
Gudebrod 3/0 polyester 176 2 lbs. 6 oz. 4.0
UNI 3/0 polyester 266 2 lbs.  *
Montana Fly Co 3/0 nylon 135 1 lb. 9 oz. 2.2
WAPSI UTC 210 N/A nylon 210 3 lbs. 5 oz. 3.2
Gudebrod G N/A mono 210 3 lbs. 7 oz. 7.0
Gudebrod G N/A polyester 330 3 lbs. 11 oz. 3.5
Montana Fly Co N/A nylon 350 4 lbs. 4 oz. 3.2
UNI Big Fly Thread N/A nylon 440 5 lbs. 4 oz. 3.5
WAPSI UTC 280 N/A nylon 280 3 lbs. 14 oz. 2.7

Bill Merg conducted the tests on 15 threads that have become available in the past several years. All of the other data listed in the chart is from the 1996 test results. He used the same methodology in testing the various new threads that have become available in the past 20 plus years, as well as the tests conducted for the thread listed in the 1996 article entitled “Testing the Ties That Bind”, that is mentioned above. On all of the tests conducted in 1995, the various brands showed remarkable consistency in thickness throughout the spool. That was not the case in a number of the threads recently entering the marketplace. Those that showed slight variation in thickness included: (variation shown) WAPSI 210 (.008), WAPSI 280 (005), and Danville 140 (006), Roman Moser Power Silk 6/0 (0012). Keep in mind that one spool was randomly selected and used for these tests.

Another thread article by Ed Engle in the spring 2000 issue of Fly Tyer entitled “Hanging by a Thread” compares twelve different threads for tying small flies. Then he rates the threads in a manner similar to how Consumer Reports evaluates products. This same article appears in Ed’s book Tying Small Flies. Ed describes the qualities of twelve threads and discusses the characteristics of each.

Darrel Martin wrote an excellent article on thread in the March/April 2000 of Fly Rod and Reel entitled “A Thread of An Idea”. He discusses silk thread and its history along with numerous facts about thread sizing, characteristics of the each material used in thread. He also comments on thread pressure applied when tying and characteristics of waxed thread. Matching the thread to the size of the fly and the material being used is extremely important in achieving both functional and aesthetically pleasing flies. The more a tier understands about all the materials used in tying the fly, the more efficient and effective fly tier he or she will become.

The newest thread to be included in this chart is Veevus, a product from Denmark.  I was able to obtain the denier on a few of the sizes, but not all of them.  The owner of the company is

not willing to release this information which is puzzling.  In those instances, I based the denier on the breaking strength of the thread after obtaining an average after 10 tests.   A majority of the Veevus threads sizes are twisted thread rather than semi-twisted or flat.  Twisted thread is stronger for the same diameter and denier than semi-twisted or flat thread.  This may explain some of the number not appearing to be accurate.  I tested the thread with the same testing tool as Bill Merg used, and I ran ten tests on each size and took as average of those ten.  Thread thickness will be entered at a later date.




Shop Thread

Roman Moser Powersilk 55 denier

This is the thread that Oliver Edwards uses to tie many of his patterns. The material is gel spun polyethylene, very fine yet extremely strong.  Breaking strength 3 lbs. 55 denier.  Colors: gray, yellow, olive, brown, black, and hot orange. Per 50 meter spool.
Price: $6.89

Giorgio Benecchi 10/0 Thread 120 denier

This is an unwaxed polyester thread .  For larger dry flies, nymphs, streamers, and small salt water patterns. Breaking strength 1 lb. 6 oz. Colors: black, white, light dun, sandy, olive, light tobacco, dark tobacco, copper, brown, red, yellow, blue, magenta, blue, pink. Per 100 meter spool.  Lays flat.
Price: $3.50

Roman Moser Powersilk 150 denier gel spun

Breaking strength 5  1/2 lbs. This thread is for very large saltwater patterns. Colors: light fluorescent green and fluorescent yellow. 150 denier.   Per 50 meter spool.  Roman sizes this thread 1/0. This thread could be used for hair bugs and large saltwater patterns as well as for attaching lead bar bell eyes to your hooks.
Price: $6.89

Danville Flat Waxed Nylon 210 denier

For saltwater patterns and deer hair work.  Colors: black, white, gray, light olive, yellow, chartreuse, orange, signal green, fluorescent pink, fluorescent yellow, fluorescent orange, fluorescent fire orange, red, blue, and brown. Waxed.  Breaking strength 2 lbs. 14 oz. Per spool.  Prior to gel spun thread this was used by many hair bug tiers, and there are still one or two that use it.  If you use small clumps of hair ( a pencil or two in size) it will probably work and you might break it every now and then.  This thread is excellent for larger streamers, saltwater patterns, etc.
Price: $1.65

Wapsi Gel Spun Thread 100 Denier

colors: black, white, yellow, olive, red, and orange. Per 50 yard spool.
Price: $3.35

Montana Fly Company Premium Thread 72 denier

Manufactured in Italy.  I've tested this denier thread on a number of different materials where extra strength is required and it is impressive. It appears smaller than typical 72 denier thread and exhibits a very high strength level.  As with most polyester and nylon threads around 70 denier the breaking strength teated 14 ounces.   Suitable for tying from sizes 6-18 dry flies and nymphs. Colors: black, white, light olive, olive, dark olive, light brown, purple, brown, dark blue, dark gray, fluorescent orange, chartreuse, cream, yellow, orange, sand, rusty brown, fluorescent fire orange, fluorescent red, grey, dark olive, fluorescent pink, fluorescent yellow, green, brown, red. It is my suspicion that this thread is the same as the Benecchi thread.  Per spool.
Price: $1.50

Uni Thread Single Strand Floss 600 denier

High quality floss for general tieing. Can be divided with a fine point bodkin for smaller fly bodies. Color: white, bright yellow, rusty orange, orange, pale blue, silver doctor blue, purple, dark blue, black, brown, red, wine, gray, green, olive, pink, royal blue, and green highlander. Best to apply with a large tube standard bobbin.  600 denier. Per 15 yard spool.
Price: $1.50

Montana Fly Company Premium Thread 135 denier

This thread is made in Italy.  I am quite sure that the manufacturers is Textreme, the same company that made the Bennechi thread.   Lays flat. This thread is suitable for tying Clouser minnows, larger saltwater patterns, pike flies, large nymphs, etc. Colors: black, white, grey, red, orange, fluorescent orange, fluorescent pink, and fluorescent yellow. Per 100 yard spool.
Price: $1.50

Gudebrod Thread Waxed 8/0 67 denier

Since Gudebrod ceased their fly tieing products in 2006 my inventory has been slightly reduced.  The following colors are remaining in this size using The Borger Color System numbers: 33 dark olive, 30 olive, 45 yellow, 77 orange, 108 gray, 107, white, 63 light rusty brown, 67 olive green, 124 purple.  Per 100 yd. spool. Note:  I have a number of Gudebrod 8/0 black thread in 300 yard spools for $2.59. The spool size is the same as the 100 yard spools.  
Price: $1.50

Benecchi Ghost Thread 60 denier

A clear monofilament thread for tying small dry flies and saltwater patterns where a clear head on the fly is desired. 60 denier. Thickness .004. 100 meter spool.
Price: $2.00

Wapsi UTC Gel Spun Thread 200 denier

As with all gel spun threads, this is continuous filament thread that lays extremely flat. Bass bug tier Pat Cohen from New York likes this size gel spun thread.  Colors: black, white, fluorescent chartreuse, and brown. Breaking strength 12 lbs. Per 50 yard spool.
Price: $3.35

Uni Thread 3/0 Mono Thread

(180 Denier) A flat polyester thread for large nymphs small to medium saltwater flies and light deer hair work. Waxed. Breaking strength 2lbs. 1 oz. Colors: black, white, gray, yellow, olive, brown, and light Cahill. Per 100 yard spool.
Price: $2.00

Cobweb Thread 134 denier

Imported from England.  A twisted thread for tiers tying medium to small hair flies such as "The Skunk." Colors: black, white, brown, olive gray, and claret. Per 10 meter spool. Being twisted provides considerably greater strength than a thread that is semi-twisted or flat.  Note the denier is only 134.  It is a couple of pounds stronger than a flat 140 nylon or polyester.  Breaking strength 4 lbs. 3 oz.  Per 100 meter spool.
Price: $2.50

Gudebrod "G" Thread 303 denier

Gudebrod ceased their fly tieing production in 2006.  The following colors are remaining of the "G" thread.  Using The Borger Color System the colors are:  20 light olive green, 19 bright green, F77 fl. orange, 108 gray, 87 light brown, 66 rusty brown, F85 fl. red.  The breaking strength is 2 lbs. 6 oz.  Per spool.
Price: $1.50

Giorgio Benecchi Ultra Strong Thread 55 denier.

Breaking strength 3 lbs. plus. Gel spun Polyethylene material. White only. Per 50 meter spool.  This is my favorite for doing medium size small hair flies.
Price: $4.50

Uni Products Glo Yarn

This white phosphorescent yarn emits light in total darkness for up to three hours. The phosphorescent material is extended into the fiber so that it cannot be washed out. Uses include trailing shucks tags bodies wing cases, etc. Per 7 yard spool.
Price: $1.00

Giorgio Benecchi 12/0 Thread 70 denier

This is one of the more popular threads with my customers.  It is unwaxed polyester made in Italy.   A good choice for midges, dry flies, nymphs, small salmon flies, Carrie Stevens streamers or any other patterns where the bulk must be minimized.  Colors: black, white, light dun, olive, dark dun, sandy dun, green, dark green, light yellow, brown, orange, wine, red, pink, tobacco, emerald, light tobacco, damsel fly blue, dark blue, magenta, and dark brown. Breaking strength 15 oz.  Per 100 meter spool.  Semi twisted and lays flat. Giorgio Benecchi closed his wholesale materials business in December 2012.  There is a fairly good supply remaining of this size thread.
Price: $3.50

Micro Floss

Fine single strand floss. Colors: black, white, red, purple, peacock, blue, insect green, olive, yellow, and turquoise blue. Per spool.
Price: $1.50

Danville 140 Denier Flymaster Plus

This version of Flymaster Plus is finer than the standard 210 denier Flymaster Plus. The thread is nylon and has 25% stretch. Breaking strength approximately 2 lbs. 12 oz. It lays flat and does not bulk up. Colors #1 white, #2 cream, #4 pale yellow, #7 orange, #31 gray, #41 beige, #47 tobacco brown, #52 wine, #56 red, #60 olive, #61 light olive, #73 dark brown, #92 purple, #100 black, # 501 fluorescent red, #502 fluorescent yellow, #503 fluorescent orange, #504 fluorescent green, #505 fluorescent fir orange, #504 fluorescent blue, #508 fluorescent pink, and #901 peacock.  Excellent for streamers, saltwater patterns, Humpy dry flies in size 12 -16.  100 yard spool.
Price: $1.65

Gudebrod Thread Waxed 6/0 143 denier

Gudebrod stopped their fly tieing operation in 2006.  These are the remaining colors of have of the 143 denier thread.  The Borger Color System are included:  118 black, 30 olive green, 87 light brown, 39 light yellow, 105 light gray, 98 brown, 20 light olive green, 63 light rusty brown, 119 dark gray, F77 fl. orange, 85 fl. red, 94 tan, fl. scarlet, 66 rusty brown, 65 dark rusty brown, f 21 fl. chartreuse.   Per 100 yd. spool.
Price: $1.50

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