We have upgraded the SKB-1904 caster kits for Rack cases and the SKB-1916 caster kits for Shock Rack cases. The new Rotocaster kits are upgraded to rotationally molded Linear Low Polyethylene for durability, include 3 inch wheels, molded in handles, molded insets and ribs for secure stacking with Standard and Roto Racks. The molded in handles also act as a bumper for stacked racks. The Rotocaster kits are lightweight, easy to handle and will not splinter or break.