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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

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

Uni Stretch Poly Floss

Single strand floss for use in steelhead and salmon patterns or any patterns where floss is desirable. 30 yards per spool. Colors: black, chartreuse, Chinese red, silver, doctor blue, purple, fuchsia, green, hot pink, orange, white, yellow, light gray, wine and pumpkin. Per spool.
Price: $1.25

Giorgio Benecchi Ghost Thread

This is a 60 denier clear monofilament thread.  Used on various saltwater pattens.  100 meters per spool.  Thread thickness is .004.  Each.
Price: $1.75

Giorgio Benecchi Polyfloss

Small size colors: with, black, light dun, red, dark orange, orange, yellow, moss green, pink, fuchsia, purple, electric blue, opal, and light purple. Per spool.
Price: $2.25

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

Uni Underbody Wrap 560 denier

A flat  nylon used to wrap flat, smooth underbodies on any streamer, classic salmon fly, or nymph hook. Use before wrapping tinsel or other material for the outer body. The material is a heavier version on Unit-Stretch. Lays flat and tapering bodies is easy with this material.  Color: white. Per 30 yard spool.
Price: $1.50

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

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

Montana Fly Company Premium Thread 350 denier

Lays flat. A continuous filament thread. Although the folks at Montana Fly Co. call this a streamer thread it has a number of other uses such as building underbodies on salmon flies, large nymphs, blue water flies, and even spinning deer hair. It is almost like a floss that could be used in place of rayon four strand floss since it is easy to apply with a bobbin. If you want to establish a large haed on a streamer to make putting on 3D or solid plastic eyes this thread is a good choice. Colors: black, white, red, chartreuse.  Lays flat.  Per spool.
Price: $1.50

Danville 6/0 70 denier

The old standard in the fly tieing industry that has been around since the 1930's. Nylon that lays flat.   Appropriate for medium to large dry flies, nymphs, streamers and Atlantic Salmon flies. Breaking strength 11oz. Waxed colors: black, white, olive, light olive, orange, beige, pale yellow, cream, peacock, charcoal, dark brown, purple, gray, tan, tobacco brown, primrose yellow maize, red, burgundy, fluorescent orange, fluorescent yellow, fluorescent white, fluorescent green, fluorescent red, and fluorescent pink. 70 denier. Per 200 yard spool.
Price: $1.60

Euro Thread

From Cascade Crest Tool. A 45 denier thread in polyester. A very good substitute for Gudebrod 10/0. 100 yard spool. Colors: light yellow, red, gray, golden yellow, black, white, olive, tan, brown, orange, green, and chocolate brown. Per spool.
Price: $2.25

Uni 210 Denier Nylon Thread

Lays extremely flat excellent for streamers, tying bass bug tails, tube flies, etc. Keeps bulk to a minimum. Breaking strength approximately 3 lbs. Stretch is approximately 25%. Colors: black or white. 100 yard spool.
Price: $2.00

Lagartun French Silk Floss

Colors: white, lemon yellow, orange, kingfisher blue and black. Per 8 yard spool.
Price: $5.08

Montana Fly Company Premium Thread 110 denier

Suitable for tying dries, nymphs, and streamers in size 2-10. Colors: black, white, olive, cream, gray, pale yellow, light brown, light olive, rusty brown, brown, sand, orange, fl.yellow, dark brown.  Lays flat.   Per 100 yard spool.
Price: $1.50

Pearsall's Gossamer Silk Thread

This thread is on small spools requiring use of a Wasatch Micro Bobbin or similar bobbin. Colors: black, white, java brown, purple, brown, light olive, gray, jasper, lemon yellow, golden yellow, pale yellow, amber, olive green, scarlet, hot orange, claret, and antique gold. Per spool.
Price: $3.98

Danville Ultra Fine Mono Thread

A fine clear mono thread. Diameter .004" - 100 yard spool.
Price: $1.50

Lagartun Silk Floss

Made in France.  Silk floss for salmon flies, traditional wets, and tags on various patterns. Colors:  white, black, red, silver doctor blue, kingfisher blue, orange, green.  8 yards per spool.  
Price: $5.08

Dynacord Gel Spun (Dynema) 150 denier

This was the first gel spun thread I was introduced to about 1987.  It was the only gel spun thread available for hair bugs for a number of years, as gel spun took about 15 years to catch on with fly shop shops and tiers.  Dan Bailey's Fly Shop was the first to introduce this thread.  After a number of years of trying to get fly shops to carry it, they dropped the line.  I bought it directly from RST in Germany.  Stronger than Kevlar® and none of Kevlar's negatives. 150 denier.  Only colors remaining: gray, red, orange, blue/green. Breaking strength 7 lbs. 9 oz.  Per 50 meter spool.  Because so many different deniers of gel spun are now available through wholesalers in the US I no longer order from RST.
Price: $5.00

Pearsall's Gossamer Pure Silk Floss

Colors: white, scarlet, olive/green, brown, highlander green, hot orange, lemon yellow, black #9, and Primrose yellow #3. Per spool.
Price: $3.98

Giorgio Benecchi Iridescent Thread

This is a metallic type thread that can be used for wrapping bodies or heads on larger patterns ribbing, etc. twisted. 30 meters. Colors: olive, rainbow, white, light pink, orange, yellow, hot orange, red, violet, indigo (dark blue), light lilac, peach, light olive, and sapphire. Per spool.  This material is the same product as the "Midge Body Thread" list in this product category.  The colors are more geared to trout pattern with the Midge Body material.
Price: $2.79

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