45 degree chamfered on two corners
A square nut having a concave face and a concave or slotted top.
NSN 6645-00-337-8276
NSN 5975-01-036-3507
NSN 6650-00-913-8405
NSN 6110-01-154-7066
NSN 5996-00-723-6743
NSN 5905-01-145-4473
NSN 7035-01-588-8470
NSN 5999-00-285-2987
NSN 5835-00-847-7277
NSN 5996-01-513-9656
NSN 6110-00-589-3134
NSN 6220-01-152-2637