Quick-disconnect locking brackets: * Secure the rack to the doorframe, but allow easy removal * Do not interfere with the normal use of the door * Fit any standard wooden doorframe Standard Gravity boots: One size fits most A Note About Boot Sizing: The Standard Gravity boots are included in this system. Standard gravity boots fit most sizes. The Gravity Boots XL (sold separately) were designed primarily for people with larger ankles/calves, not necessarily larger feet. The diameter of these XL boots is 1 inch larger and the height of the shell is 1 to 1.5 inches taller than the standard boots. Both boot sizes are designed to provide an ankle-conforming fit through two "fine-tuning" buckles with micro-adjusting ratchets that fit the exact size and taper of your ankle. The fit accommodates a wide range of sizes, making it possible for multiple users to share one pair of boots. * Double-bar system: Easy mounting and dismounting * High-quality finish: Scratch-resistant coating * Door-saver: Protects doorframe from damage while in use * Foam hand grips: comfortable and secure grip * Gravity boots: soft foam liners and flexible shell * Instructional DVD and 90-page book Better Back, Better Body * 5-Year Warranty * 30-day money-back guarantee * Meets all UL safety requirements