55X Stock Adapter

SIG 55X Picatinny Stock Adapter

This adapter allows you to mount the popular Magpul/KDG ACR stock on your SIG SG550, SG551, SG552, SG553, SG556, or SG522. The telescoping stock with cheek rest offers many additional adjustment options, allowing you to configure the rifle exactly to your needs.

The hinge features a built-in locking mechanism that ensures the stock stays folded when necessary without compromising functionality.

The design is the lightest, yet just as strong—or stronger—than other options on the market, and given the global shipping issues with the ACR stock following its discontinuation, this will likely be the last batch we’ve produced. The adapter is CNC-machined from aerospace-grade aluminum and anodized matte black to Mil-Spec Type III Class 2 standards.