Magpul MAG470-GRY STR Carbine Stock Stealth Gray Synthetic for AR-15, M16, M4 with Mil-Spec Tube (Tube Not Included)Made in the USA, the Magpul STR (Storage Type Restricted) is a drop in replacement buttstock for AR15 M4 carbines using mil spec sized receiver extension tubes. A storage capable version of the CTR, the STR has improved cheek weld and two water resistant battery tubes on a compact, reinforced polymer A frame design. The STR incorporates two integral sling loops, a reversible push button QD sling mount, and a replaceable 0. 30" thick rubber butt pad