Vortex G6A3 Flash Eliminator with 10° Pitch and Helical Grooves Especially designed to make the SEI Sound Suppressor easier to remove, featuring a shallower pitch and grooves to reduce surface contact and carbon buildup. Heat treated same as all other Vortex's. 1/2 x 28 I.D. thread. The world’s best flash suppressor for the M16-AR15 family of firearms, now available for use with SEI Direct Connect (DC) Sound Suppressor. Threaded 1/2 x 28 x .625-.630±” thread depth. NOTE: Do not use this part on a 7.62mm/.30 cal. barrel that may also have a 1/2 x 28 thread! Be sure your manufacturer or armorer has provided you with the correct part.