UNI BigFly Fly Tying Thread - Designed specifically for big saltwater flies, bass bugs and other tying applications where a very strong, easily-handled thread is necessary. Same material (polyester) as UNI 6/0 & 8/0 so it won't dull fly-tying scissors. 4 times stronger than a 6/0 thread and four times bigger too. Untwists quickly and easily for flat-thread applications. 80 yard spools available in all the right colors. Continuous polyester filament 400 denier size 80 yard spool