Safety switch with key assembly used on True Fitness models: 300, 300P, 300HRC, 450, 450P, 450HRC-SS100, 500, 500P, 500HRC-SS100, 450, 450P, 450HRC, 350, 350P, 350HRC, 350PB, 350HRCB, 500 (00) 500P (00), 500HRC (00), 500CI (00), 750CI, 750HRC, 750P, 500A, 500AP, 500AHRC, 525P, 525HRC, 525CI, 550P, 550HRC, 550CI, 600, 600P.

This new Switch comes with the Smaller version of the saftey key that fits.