3 thread class right-hand 56 thread quantity per inch nut, plain, hexagon cres type: 302 per ams 5688, ams 5636, ams 5637, or ams-qq-s-763; 303 per ams 5640, astm A581, or astm A582; 304 per ams 5647, ams 5639 or ams-qq-s-763, per astm A276, or ams-qq-s-763, 304l per astm A493, ams 5647 or ams-qq-s-763 phosphate nut surface treated