Material:Cover is the Dupont Surlyn, Innermost layer is Synthetic rubber Color:as the picture show Weight:approx 38g/pcs Elasticity:above 70% Hardness:80% Package: 1pcs ball in the bag Features: 1) you can see whether your swing is right or not from the path as it rolled. 2) it rolled straight means that your alignment and stroke were square. 3) it curved inward, towards you means that your club face was slightly closed at impact. 4) it curved out and away ,that means your club face was slightly open at impact. 5) force you to hit square and center on club face. 6) inaccuracies send it wobbling,rolling at a curve or falling on its side. 7) cambered sides for precision, performance added training capabilities.