Part Numbers: 1000105094 or 1000110297. This safety key fits multiple Johnson treadmills including but not limited to these model numbers: TM625, TM639, TM660, TM633, TM635, TM626, TM655, TM621, TM659, TM734, TM622, TM623, TM643, TM644, TM659B, TM381, TM637, TM652, TM380, TM397, TM451, TM667, TM397B, TM400, TM444B, TM475, TM475C, TM476, TM444, TM458, TM459, TM428, TM705B, TM406B, TM407B, TM423, TM424, TM438E, TM439E, TM438, TM438C, TM439, TM439C, TM450