RIO's Fluoroflex Strong Tippet material is an ultra-strong, 100% fluorocarbon with exceptionally high tensile strength. The material is very easy to tie knots in, with high knot strength and a smooth finish that ensures knots seat easily and tightly. The high break strength to diameter ratio makes this a fantastic fluorocarbon for the trout fly fisher. This tippet offers 'half sizes' of core trout diameters, giving anglers an extra choice when faced with the decision to choose between, say 4X and 5X. Each spool has 30 yards of top quality material spooled on. '3-Packs' also available in select sizes, 30-yard spools of tippet packaged in a reusable, clear plastic cup.