Axle Shaft Hub Adapter 21mm for 13/16" Axle & 35mm M35 Thread Free Wheel Ratchet adapter Drive w Threaded w set screw. Family sprockets and axle hub adapters. Please choose adapte size , sprocket size or combination. These sprocket wheels are designed to be used with #25 roller chain which is 1/4" pitch. These are commonly used in Go Karts, ebike, electric minibike & Scooters. Chain wheel sprockets are made of steel and are nickel plated. There is a free wheel adapter, so traction will only be applied when motor is doing work but will roll free when not using motor and the hub axle adapters are also made of steel and come with a set screw to lock to the shaft or axle. The hub adaptor is a little bigger than the shaft so it goes in smoothly but has a tight fit.