Our Perfect balance Technology. Comes with 2 sets of removable 1/2 inch full visco inserts which offer increased protection for your horses back. Visco Foam will even out minor contact issues as it contours to horses' toplines Front pockets designed to accomodate optional visco wither inserts. Rear of pad will fit optional visco back risers. Sizes Medium fit saddle sizes 17 to 17.5 and Large 17.5 to 19.