This Four Speed Transmission Mainshaft Nut Wrench Adapter works with a 3/8" ratchet to loosen and tighten Harley-Davidson 4-speed mainshaft sprockets. It was designed to pack flat in your tool box or you can throw them in your tool bag for on the road repairs. Don't use that crescent wrench! Beefy 1/4” stainless steel, made in Ohio.