This is grippy resin material. We develop this article for medicine ballInner core is very special to keep its shape. Correct weight, and very balanced medicine ball.Aramid grippy material.This is bulletproof material same as bulletproof jackets. Very grippy outer surface, low bounce, inner core material is also special developed so medicine ball can keep shape round after use. This is burst proof medicine ball. You can use as slam ball, wall ball. Heavy weight from 2Lb to 200LB is available. Also we can make heavy bags from this material if needed.