Long Spine Immobilization Board The BAK-PAK II™ Long Spine Immobilization Board was designed by an EMT and constructed by a mechanical engineer with the intention of making a board where every inch, every contour and every feature will serve a purpose. The BAK-PAK II™ spine board is constructed of LLD polyethylene, and is foam-filled - making it great for water rescues! Guaranteed not to crack, splinter or chip. The convex bottom’s built-in runners provide raised access to the easy-grip handles.