Losi Night Crawler 2.0 HD Worm Gear Set. These are compatible with the Night Crawler and Night Crawler 2.0 models, as well as the Comp Crawler. The worm gear acts as a break when no power is supplied. When power is supplied, axle torque is optimized so the vehicle won't be thrown off-balance while climbing. The small gear assembly provides extra ground clearance beneath the axle housing. Package includes a worm drive gear set for the front and rear axles, as well as a shim set and a tube of black grease.