The Hybrid Collapsible Stock serves to break the barriers of traditional air through and air in stock systems by enabling a user to seamlessly switch between using a 13 cubic inch air cylinder or a remote line. Adding to its unparalleled functionality, the HCS also offers all of the cosmetic and ergonomic benefits of some of the most popular firearm configurations for unbeatable compactness and close quarters performance. With the included remote airline fitting, you will have the ability to swivel the fitting on the bottom of the stock. This fitting will accept any 1/8"NPT air fitting. The HCS is compatible with the Valken M17.