This is the optional Ball Diff for the HPI Sprint. The preassembled Diff is ready to install in the front or rear of the Sprint.FEATURES: Hubs feature metal construction Fully adjustable for fine-tuning to track surface Pulley features plastic construction Black in colorINCLUDES: One assembed ball diff One instruction sheetREQUIRES: Installing into vehicleSPECS: Pulley Specs 32 teeth Diameter at teeth: 30mm (1.18") Overall Length: 59mm (2.322")COMMENTS: For Maintenance Set, order HPIC2048 NNA 4/6/03 ir/jxs