Factory preassembled and ready to rock and roll! When driving is more important than tinkering, this is the way to keep up with the fast paced world. Please see page-22 in the Hellfire Instruction Manual for wire-diagram details.This differential kit includes every part listed to make your spare time spent driving instead of assembling:#B085500 DIFFERENTIAL CASE#B085500 METAL INSERT FOR DIFFERENTIAL CASE#86032 BEVEL GEAR (P1x20T/SINTERED METAL) #86099 DIFF CASE WASHER 0.7mm #86520 DIFF SHAFT 13x30mm #86521 BEVEL GEAR P1x10T (MODIFIED 86033) #86522 BEVEL GEAR 42TOOTH #33406 SHAFT 4x27mm FOR 4 BEVEL DIFF #87352 WASHER 4x10x0.15mm #6811 O-RING 6x9.5x1.9(Black) #B085 BALL BEARING 8x16x5mm #Z085 FLAT HEAD SCREW M3x15mm (HEX SOCKET) #Z164 HEAVY DUTY GREASE #Z260 PIN 2.5x12mm #Z721 SET SCREW M4x4mm #Z904 ALLEN WRENCH 2.0mm