The M351KT provides the tools patients need to perform key exercises to stretch upper back and neck muscles with this complete kit. The M351KT kit includes head strap that adjusts from 20-26in/50-66cm, door mount and 2ft/60cm modular tubing with 1.5-4.5lbs (0.5-2.0kg) resistance. Resistance when stretched 1-3 times original length. Interchangeable.