Balancing out the end of the carbine is the Vltor Modstock. This is used in place of a standard ribbed stock. The Modstock gives a QD mount, as well as battery compartments to hold either “AA” batteries, or the CR123 batteries that most weapon mounted lights are now using. The battery storage compartments extend out, and give an increased cheek weld. The compartments are waterproof, and can be removed without removal of the stock. Built into the stock are ambi-quick disconnect mounts to allow for any QD equipped slings to plug in. The battery compartments also make for an substantially increased cheek weld when compared to standard carbine stocks.