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. 100 yard spools available in all the right colors, 11 total. Black, Chartreuse, Dark Brown, Fire Orange, Gray, Olive, Orange, Pink, Red, White, Yellow.