IF THIS DOESN'T FIT YOUR MACHINE PLEASE CONTACT US AS WE'RE HERE TO HELP. TreadLife Fitness Key for some True Treadmills / Part # 90177400 / True makes A LOT of different keys for their different models, their is no such thing as a universal key. / Please check the models listed to make sure this will work on your treadmill. / WORKS ON THESE MODELS: 300HRC, 300P, 350 Black, 350 Black - Rev. A, 350HRC, 400HRC, 450, 450HRC, 450P, 500 - AOP, 500 ss100, 500/5 - 500/5, 500A, HRCO - 95-97, 500SE/5 Treadmill - 500SE/5, Z5R - TRZ50001. COLOR: These come in black or red color clips, we send out RANDOM. The key insert is identical