4 pcs hex nut
These Nuts are part of a simple, very effective, method of joining the Axle to the Wheel with absolutely no slippage. This nut has a slot built into one side of it, and that slot fits over the Axle Pin, keeping the pin in place. This Nut will now spin with the Axle. The Wheel has an impression of the Hex Nut built into the Wheel that the Hex nut fits perfectly into when the Wheel is applied to the Axle. When the Wheel Nut is secured onto the Axle and tightened down, the Wheel will now spin with the Axle and never slip.