This kit allows the upper receiver of an MCX to be combined with the lower receiver of an AR-15 in .300 Blackout. This kit includes the upper receiver of a Sig Sauer MCX, an AR 2 stage Matchlite DUO trigger, a 90 degree muzzle adapter, and an X-Fold stock adapter, an MCX to M400 lower receiver adapter. The MCX operating system is unique in the fact that it doesn’t need the long buffer tube found on standard AR variations. This is due to its one of a kind internal recoil and short-stoke operating system and allows for an X-Fold folding stock to be installed.

Kit includes:

• Sig Sauer MCX upper receiver
• AR 2 stage Matchlite DUO Trigger
• 90 degree muzzle adapter
• X-Fold stock adapter
• MCX to M400 lower receiver adapter
• 16” barrel