This is a optional Robinson Racing "Hi-Performance" .8 Mod Steel Slipper Kit, and is intended for use with the Traxxas Slash. Robinson Racing GEN3 Slipper Units are over-engineered to meet the punishing demands of the most powerful brushless motor systems! GEN3 Slipper Units will not fail under the enormous load conditions of today's brushless motor systems. The new GEN3 Slipper Unit is a captured design to prevent slipper pad blowout and deliver maximum power to the ground. The hi-performance hardened steel spur gear will not fail or strip. Strong and tough 0.8 module/32-pitch teeth handle all the power you can pour on the spur gear. Aircraft grade billet aluminum backplate will not bend or break. Increased surface area of the oversized pad insures dependable performance. Less total parts reduces flex and wobble in the spur gear and slipper unit. Bearing included.