45 degree chamfered on two corners
A square nut having a concave face and a concave or slotted top.
NSN 5930-00-372-5642
NSN 5985-00-542-0597
NSN 6150-01-512-1142
NSN 5910-00-060-1367
NSN 6685-00-024-5186
NSN 5999-01-364-8500
NSN 5935-01-633-5082
NSN 6620-01-482-9024
NSN 4140-01-353-9043
NSN 6110-00-248-7475
NSN 5930-01-097-5910
NSN 5998-01-168-8953