If you have lost safety keys or you simply want to purchase treadmill replacement parts, you can buy one directly from LifeSpan. The rectangle prong replacement treadmill key works with the following LifeSpan products: TR1200i Treadmill (2015 model and earlier) TR3000i Treadmill (2015 model and earlier) TR4000i Treadmill (2015 model and earlier) TR5000i Treadmill (2015 model and earlier)