Leatt Z-Frame Knee Brace Pair - BlackMEDICALLY CERTIFIED PROTECTION We learned a lot from developing our C Frame and X Frame knee braces, and we recognise the need for a cage type knee brace for junior riders. Not as stiff as the C Frame, but a good chassis made from glass filled nylon for comfort and a Carbon Injected knee for that rigidity which reduces the ACL, Meniscus, and MCL injury risk. The Z Frame is also CE certified as a medical device and as impact protection, maybe it's time