a saddle tree, a seat fixed to the tree, said seat having a front attached to a pommel and a back attached to a cantle, said tree consisting of two bars, each of which has an underside, a pad with a top face that extends along the underside of the bars, a plurality of shims interposed between the pad and underside of the bars, each shim having a top and bottom face, said shims being of various sizes, shapes and thickness selected and located to adapt to the contours of a particular horse in order to distribute the pressure of the saddle more uniformly on the back of the horse, said shims being removably secured to the underside of a bar of the tree by a hook and loop fastening system which interconnects the underside of the tree with the top face of the shim, said shims being removably secured to the top face of the pad by a hook and loop fastening system which interconnects the pad and the bottom face of each shim, said hook and loop fastening systems being capable of maintaining the shims in the locations selected on the underside of the saddle when the saddle is on and off of the horse, said shims being easily removable for the placement of shims of different shapes, sizes and thickness selected and located to adapt to the contours of a different horse.