Upgrade your MVB MPK to a SBR (after receiving your stamp) or simply upgrade your 2 position or multi-position stock (purchased prior to December 2016) to the 2017 ARC-X stock model, which is dropped tested to 6 ft. and has an improved locking mechanism.  You can also upgrade to an ARC-Xti with titanium rails and skeletonized butt pad and base block.

Kits includes complete stock assembly excluding buffer tubes, buffer, and springs.  The stock assembly consists of base block, rails, buttpad, and locking mechanism.