10-inch: Compatible with X8 and/or X7 10-inch models.  Front wheel motors are 350 watts (that can maximize up-to 700 watts) and come preinstalled with 10" air-filled tubed tires. 

8.5-inch: Compatible with X7 8.5-inch models.  Front wheel motors are 350 watts (that can maximize up-to 700 watts) and come preinstalled with 8.5" air-filled tubed tires.

5.5-inch: Compatible with X6 models. Front wheel motors are 250 watts and come preinstalled with 5.5” solid rubber tires.