Types include molded, cleanout & ball mill. Standard sizes of 5/8 in., 7/8 in., 1 in., 1 3/8 in., 1 5/8 in. & 2 in. balls. Made of natural rubber, neoprene, Buna-N®, silicone & EPDM balls. Specifications of rubber balls include 150 degrees F to 425 degrees F operating temperature. Rubber balls are oil, tear, abrasion & fat resistant.