Used on mrap - common nsn - 2 mrap variants and 1 other weapon system. 3b thread class right-hand 12 thread quantity per inch nut, self-locking, extended washer, double hexagon, 220 ksi, 450 deg. f. material: alloy steel, 17-22a (uns K14675) per AMS6304, or 8740 (uns G87400) per AMS6322. /9/