Our patented Anatomical Carbon-Matrix frame is a Carbon fiber, RIM (reaction injection molding) process. Inside of our anatomically correct molds, a two-part, foam/epoxy is injected through and around the carbon fiber braid. This results in a lightweight, extremely durable, foam core carbon fiber sandwich structure. The upper frame is designed to accommodate the dynamics of the leg musculature, allowing the muscles to flex and relax without interference. Not only does this design keep the frame properly positioned on the leg, it does so without constricting the muscles as they change when the leg is in motion. The lower frame is shaped to capture the tubercle (top of the shin bone), just under the knee joint. This design, in conjunction with our Anti-Rotation Tether feature, is a must in order to help protect against lower leg rotation.