Adaptable Carbine/Storage (ACS) stock is a drop-in replacement for standard USGI M4 collapsible stock that gives the tactical operator extra storage options, a secure, comfortable cheekweld, and an advanced dual-locking lever. Smooth, streamlined exterior contours prevent snagging on clothing, sling, or vegetation, and helps ensure fast exits from vehicles without snagging on gear. Removable battery storage compartments run the full length of the extra-wide comb and hold 2 AA or 3 CR-123 batteries, while providing a wide, contoured area for an exceptionally solid, comfortable cheekweld. Secure molded rubber caps keep water and dust out of compartments and face the rear of the stock for easy removal; cap exterior is beveled to resist snagging when shouldering weapon. Positive-locking trapdoor on right side of the stock reveals a roomy storage compartment for additional batteries, coiled up cleaning cable and other cleaning supplies, ear plugs, spare parts, or other small items. Magpul?s dual locking system uses an additional cam lever to protect the release lever from accidental operation, yet still allows you to adjust length of pull by simply pushing on the release lever. Slot molded in the toe provides an attachment point for a 1�" wide sling. Also includes the same detachable rubber buttpad found on Magpul CTR and UBR buttstocks to help keep stock firmly mounted on shoulder. Mil-Spec fits 1.14" O.D. buffer tubes on Colt-manufactured M4 and similar mil-spec tubes that accept both four- and six-position collapsible stocks. Commercial fits larger, 1.17" O.D. commercial carbine buffer tubes. Buffer tube, carbine buffer, receiver extension nut, and carbine-length action spring not included