The Magpul PC BackPacker has a drop-in design compatible with all factory Ruger PC Carbine models offered in 9mm Luger and 40 S&W. Features a unique locking interface to attach the barrel assembly to the stock body when being transported, ergonomic M-LOK-compatible hand guard, water-resistant grip storage compartment and a second compartment in the riser section, optional QD sling mounting capability and MOE SL nonslip rubber butt-pad; compatible with the MOE SL Enhanced Rubber Butt-Pad (MAG349) for an additional 3/8″ LOP and enhanced user comfort. Includes interchangeable standard and optic-height cheek risers.