These keys are a standard size for various Proform, Weslo, Weider Weslo, Lifestyler, Image, Healthrider, Good Family, Reebok, NordicTrack, Gold's Gym and Cardiotrainer Treadmills. Part number 119038 and 119039. Maintenance Tip: Annual walking belt lubrication with our World Famous Treadmill Lube will help prevent damage to the motor and other expensive electrical parts.