Polarstar Aluminum UGS End Plate Assembly

Your M4 lower has a hole on the side for the end plate. On an AEG, it holds the buffer tube and passes the trigger-group wiring. On a Polarstar UGS build, it does something different.

The Polarstar UGS End Plate Assembly is the interface between your rifle receiver and the Unified Gas System. Machined from aluminum, it takes the place of the standard end plate and gives you a dedicated mounting point for the UGS air line and stock rail. One pivot screw, one end plate — that is what is in the box.

What it enables. If you are running an original Polarstar UGS on an M4-series platform, this is the fitment piece that holds everything together. It also unlocks a specific conversion: R3-series rifles can be adapted for the UGS 2.000 HPA system and milspec stock rails. That means you get a proper rail interface instead of sticking adhesive rails onto the stock tube, which is cleaner, more rigid, and less likely to peel off when you should.

Compatibility notes. Cross-compatible with both Type 1 and Type 2 UGS systems. Not compatible with the HK417 UGS — if you are building around that platform, this is not the part you need.

Aluminum construction keeps weight down while maintaining the rigidity you want from a structural mounting point. The end plate is an upgrade over the factory piece, so if you are upgrading an existing HPA rifle or starting a new Polarstar build from scratch, it is a purpose-built component that improves fit and system integrity.