Designed specifically for the .223 and 5.56 mm caliber cartridge, the Eclipse Flash Hider uses a slightly twisted triple prong design to reduce flash to near zero in even total darkness conditions. The device is threaded 1/2 x 28 tpi and will clear any projectile up to .223 caliber and 5.56 mm. Do not use with larger calibers. The Eclipse Flash Hider is marked "MA” and "223” and a crush washer is included.