The Matrix Western Shim Pad has three pockets for shims to adapt the fit of the Western saddle to the horse's conformation. Each pad comes with a set of 12 shims: 2 front, 2 middle and 2 rear for each side. Strategically place the shipms to balance the saddle from front to back or adjust from side to side to compensate for asymmetrical muscle development. Easily converts from a built up to a bridge pad for use on multiple horses. The Extreme Pro Impact inserts provide a maximum impact protection using a lightweight contouring layer of high density Poron XRD. Measures 31" x 30".