We learned a lot from developing our C-Frame and X-Frame knee braces, and we recognized the need for a cage type knee brace for junior riders. The Z-Frame is not as stiff as the C-Frame, but has a good chassis made from glass-filled nylon for comfort and a Carbon injected knee. Features injected Composite chassis Slim hinges for superior bike feel Injected Composite hinge covers for rigidity and endurance Reduction of forces to limit knee injuries medical device: EU CA014741, USA FDA 10048761 Hyper extension limitations: 5°, 10°, 15° and 20° for ACL injury reduction Low-profile shin bone pad for excellent boot fit Comfortable, easy-fitting and low-profile strap system Customized fit with interchangeable hinge padding sizes Junior Onesize