These mandrels are threaded to fit on a lathe headstock spindle. They are precision machined in America by Steer Machine Tool and Die Corp. They have two opposing flats to make convenient removal from the lathe with a wrench. The mandrels have a 3/8” x 16 self-tapping thread to match the Steer Stainless Bottle Stoppers and Honey Dippers. They are finished with a rust protective black oxide coating and they are precision machined to run true to within .002” of an inch.