Forward Controls Design 6315AE 5.56 Compensator - Allen Engineering - 1/2x28 - 6315AE - $80.75 6315AE is a collaboration between Allen Engineering and FCD. Threaded for 1/2 x 28 (internal) and M22 x 1 (external), 6315AE is compatible with all Allen Engineering .223 sound suppressors such as AEM2