30Rnd. STANAG SD is a 30 round magazine holding 5.56x45mm subsonic ammunition. Due to the slower bullet, the rounds loaded in it are both more quiet and shorter range than those in the 30Rnd. STANAG magazine.
It can be used in both silenced and non-silenced weapons. When used in a non-suppressed weapon, zombies react as if it was a silenced shot, making it very useful for killing in cities. It still sounds just as loud as the normal shots to players and produces a normal muzzle flash.