These balls don´t bounce or roll!! Slam Ball training is a great way to perform exercises which involves explosive power.Training developes speed, dynamic core strenght, balance and eye- hand coordination.Slam Ball is safe to use as soft structure protects floors and feet.Available in 4kg, 8kg, 12kg and 16kg.Country of origin:China.Product (cm):23x23x23.Product (kg):4.MATERIAL:Rubber and Ironsand.