To simplify the assembly of the upper shells (back holes) of your KJ-XR3 and KJ-Pro7 models in sizes S and M, as well as the KJ Power Shoe, there is specific hardware available. This hardware set includes 2 bolts and 2 washers, which are carefully designed to securely fasten the upper shells to the rest of the shoe structure. With this hardware, you can ensure a sturdy and reliable connection for your Kangoo Jumps rebound shoes. It's worth mentioning that this hardware is also compatible with older models, providing flexibility and convenience for those who own previous generations of Kangoo Jumps rebound shoes.