T3 Forged T3C - Cast Aluminum Receiver T3 Ti - Titanium! T3MX - MaxhardŽ T6 - T3 lower and T12 flat-top upper T6MX - T3MX and T12MX flat-top T5 - T3 lower and T2 A2 upper T5MX - T3MX and T2MX MaxhardŽ A2 upper