These adaptors allow the use of standard 9/16"-20 threaded pedals with bike or exercise machines that use one-piece cranks with 1/2"-20 pedal threading.
Note: These adaptors are made by Kneesaver. They are not "Kneesaver" spacers, although they do add 20mm of extention.
Remember: The left-side cranks are reverse thread. Turn counter-clockwise to tighten.