WHPRO4X (SET of 4) Swivel Wheels Kit for RCF SUBs 100mmZinc plated, pressed steel, swivel housing, plate fitting, with double ball race. Kit no 4 swivel castor, 100mm 4 wheel with roller bearings. Compatible Subwoofers: SUB 18 AS, SUB 18 AX, SUB 708 AS MK3, SUB 8003 AS MK3, SUB 8004 AS, SUB 8006 AS, SUB 8008 AS. Product Features Zinc plated, pressed steel, swivel housing, plate fitting, with double ball race Swivel Housing: Yes Number of Wheels: 4 CE Marking: Yes Compatible Subwoofers: SUB 18 AS SUB 18 AX