Translucent round plastic nymph ribbing and body material that has many uses for segmented bodies. Soft and easy to work with. Vinyl Rib in the medium size (hook size 8-12) is good for crazy charlies, stoneflies and large nymphs. The midge size (hook size 16-20) is good for midges and small nymphs. The nymph size (hook size 12-16) is good for midge to medium nymphs.