This is the 6x19x21mm Cup Joint for use with the HPI Dual Fiberglass Brake Disc, HPIC7055. Fits the HPI Savage X and XL monster trucks Constructed of steel Cup joint with 2mm hex wrench, two screws Thread Lock, HPIR1159 Heavy Duty Grease Installing on brake assembly Length: 21mm Hex Size: 19mm Hole Diameter: 6mm Must be used with the Dual Fiberglass Brake Disc jxs 7/08/08 ir/jxs &