ATI's Omni Hybrid Multi-Cal AR-15 lower receiver features a patented hammer and trigger pin retainment system, preventing movement from the hammer and trigger pin during firing. The Omni Hybrid also features ATI's patented over-molded metal insert, which reinforces the buffer tube housing and rear takedown pin. This allows for metal-on-metal contact with both the buffer tube as well as the rear takedown pin thus increasing strength and durability from recoil and consistent firing.  NICS check applies, call Todd at REDACTED3   $96/ tax