If you have lost your magnetic safety key or you simply want to purchase a spare treadmill part, you can buy one directly from LifeSpan. The round magnetic treadmill key replacement works with the following LifeSpan products: TR2000 HR/HRC Treadmill TR2250 HR/HRC Treadmill TR2500 HR/HRC Treadmill TR3000 HRC Treadmill PRO1 Treadmill PRO3 Treadmill PRO5 Treadmill