Russian AKSu 1981-1986 muzzle brake, NOS with light storage traces.
Fittible at AKS74-U / AKSU / AK105 / Saiga and Yunker-2/ -3/ -4/ -5 (Cal. 4,5 & 6 mm BB)
The Krinkov has a muzzle booster/flash hider with a distinctive closed single chamber and conical front flash hider portion. The muzzle thread pitch on AKS-74U is identical to that of the AK-74. The Krinkov muzzle device also has notches on the conical portion to allow using a tool to make a handle and use the advantage of the leverage if the muzzle device is stuck.
First Krinkov muzzle devices were made by IzhMash and had a smooth body. Later, both Tula (1982-1986) and Izhevsk (1981-1986) plants switched to manufacturing the second pattern muzzle device (left one on the bottom row) which has a relief in the middle portion. From 1987 to 1993 the third pattern was introduced which differs from the second pattern only by the lack of the rear beveled surface.