Custom Solid Back Insert, 15" to 20" in width and height, made of a ½" of HDPE (High Density Polyethylene), a foam module (Medium Package 1" Soft Sunmate on½" Medium Sunmate), a zippered Black Neoprene (Rubatex) cover and secured by depth/angle adjustable steel mounting hardware (standard duty 4ea. L-Brackets w/4 holes, 4ea. J-Hooks w/1 countersunk hole & 4ea. horseshoe clamps for 1" tubing ). (T-Nuts installed to accept a pair of aluminum tracks for future mounting of Lateral Trunk Supports and Lateral Hip/Thigh Supports)