This kit uses the OE factory upgrade for the 8" tri-hub rear axle common on the 2018 and prior sleds that came equipped with only the inner wheels.  This new style axle has the wheel bearings pressed onto the axle.  With this configuration, should an axle bolt start to loosen the wheels stay fixed to the shaft.  With a sleeved style fitment common on other axles, a loose bolt results in the whole assembly being loose and the wheels are loose on the shaft.  When compared to the original tri-hub design, a single bearing or wheel failure will not result in loss of function of both wheels.  It's an upgraded design that adds a level of safety.  This kit uses OE plastic wheels, bearings, axle and bolts and ships with the wheels already pressed on the axle for a quick and easy install with your exisitng axle adjustment hardware.