UNI-Thread Fly Tying Thread UNI-Thread is a continuous-filament polyester fly tying thread available in 8/0, 6/0, 3/0, and 400-denier BigFly. Together, these four sizes cover everything from low-bulk midges and dry flies to everyday trout patterns, streamers, bass bugs, deer-hair flies, pike and musky patterns, and saltwater flies. The 8/0, 6/0, and 3/0 options are waxed for secure material control at the vise. UNI’s thin waxing process improves grip while limiting the wax buildup that can collect inside a bobbin tube. BigFly uses the same basic polyester construction in a much heavier diameter and can be untwisted for flatter, smoother wraps. Which UNI-Thread Size Should I Use? 8/0 UNI-Thread: 72 denier with a nominal breaking strength of 16 ounces on a 200-yard spool. Use it for midges, small dry flies, emergers, and slim nymphs where thread bulk can change the finished profile. Its slightly bonded continuous filaments lay flat on the hook for clean, controlled bodies and heads. 6/0 UNI-Thread: 136 denier with a nominal breaking strength of 33 ounces on a 200-yard spool. This is the most versatile UNI fly tying thread for dry flies, nymphs, wet flies, and small to medium streamers. Choose 6/0 when you need dependable strength without excessive buildup on everyday trout patterns. 3/0 UNI-Thread: 220 denier with a nominal breaking strength of 32 ounces on a 100-yard spool. UNI recommends 3/0 for hooks larger than size 12. Its thicker diameter is well suited to larger streamers, bass flies, hair-wing patterns, bucktail, fur, and other materials that benefit from a broader thread wrap. UNI BigFly Thread: 400 denier with a nominal breaking strength of 100 ounces on an 80-yard spool. BigFly is built for deer-hair bugs, large bass flies, pike and musky patterns, and heavy saltwater flies. Its larger diameter helps reduce the tendency to cut through hollow deer hair under tension, while its continuous filaments untwist easily for flatter thread bases. Understanding UNI-Thread Sizing A larger thread diameter does not automatically produce greater breaking strength. UNI’s current specifications list 3/0 at 32 ounces and 6/0 at 33 ounces. Choose 3/0 when you need a thicker thread footprint and more material coverage on larger flies. Move to 400-denier BigFly when the job requires a substantial increase in holding power. Key Features Continuous-filament polyester construction Available in 8/0, 6/0, 3/0, and 400-denier BigFly Waxed 8/0, 6/0, and 3/0 options Sizes for small trout flies through large predator and saltwater patterns 200-yard spools in 8/0 and 6/0 Multiple tying colors, with availability varying by size BigFly untwists for flatter wraps BigFly’s wider diameter works especially well for spinning and securing deer hair Choose 8/0 when profile and low bulk matter most, 6/0 for all-around trout tying, 3/0 for larger-diameter wraps on bigger patterns, and BigFly when maximum holding power is the priority.
