This is a shaft and wheel set for our IG32 DM Compact ATR. The kit includes our 4" tire set and adds a custom hex shaft that is drilled to 6mm on one end and has a set screw to lock the shaft to the motor, the other end is taped thread to accept the included machine screw. The set screw clamps onto the 6mm motor shaft. This set includes 2 of everything since the tires are a matched set with directional tread.