Economy quality treadbelt used on Cybex models 450T, 500T, 515T, 520T, 530T, 550T, 600, 640, 700, 700T treadmills. With 60" walking surfaces.  Units with serial numbers GREATER than model 500T = X07-07520T9814NN, model 515T =  X07-07515T9514NN, model 520T = X07-07530T9814N, model 530T & 550T = X07-07530T9814NN