The Air Through Skeleton Butt Stock Adapter is the critical connection point between your marker and your RAP4 Skeleton Stock or UMP Stock. Designed to empower you to run your air line through the stock adapter and into your marker—rather than relying on the regular ASA and steel braided hoses—this version of the adapter comes stripped down for players who already have the 1/8” male quick disconnect and Flexi-Air Hose for their marker or simply want to install the most secure means of attaching their RAP4 Skeleton Stock or UMP Stock.