RIO Powerflex Tippet is a high knot strength copolymer nylon tippet that features superb knot strength, stretch and suppleness to make this an excellent nylon tippet material for almost all trout fly fishing needs. It  is a light grey color to enhance its camouflage ability on the water, and is available from 8X to 60 lb, 

Powerflex is available in a useful, money-saving "3-pack" option (3 regular sized spools, conveniently packaged in a handy plastic tub):

8X (1.5lb) to 0.015" (25lb) - 30 yards per spool