Shifting steel sand in a pliable, Durable DuPont™ Kevlar® fiber disc. Slightly textured and tacky to keep the disc in your hands, and the weight is embroidered on each disc. Adds a new challenge to muscles and improves grip strength. Safe for studio floors and durable enough for use outside. Twelve weight options, from 5 to 100 lbs. Part of the XD™ Kevlar® line of products.