The Body Solid GSCR349 Plate-Loaded Seated Calf Raise Machine. Made with heavy duty 3 x 2 rectangular tubing, resistance is provided by adding plates which are leveraged against the calf raise movement by a ratio of 3-to-1 - meaning for every 50 lbs of free weights added to the machine, 150 lbs of resistance is transferred to the exercise motion. The main pivot arm rides on sealed pillow block ball bearings that will last a lifetime. Shown with optional olympic plate adapter which is sold separately. Uses 1" I.D. standard plates. Other features are the adjustable, ultra-thick knee pads that protect the user's pressure points, and an ergonomically angled calf raise block with non-slip surface. Plates sold separately.