MIL-DTL-32258, DETAIL SPECIFICATION: NUT, SELF-LOCKING (RING TYPE NON-METALLIC INSERT), HEAVY HEX, CONTROLLED ROOT RADIUS, NICKEL-COPPER ALLOY (28 JUN 2007) (SUPERSEDING MIL-N-25027/1A)., This specification covers ring-type, self-locking, heavy hex, nickel-copper alloy nuts, with screw threads with a controlled root radius for use in general shipboard applications. Coarse pitch series and eight pitch series of threads are covered by this specification. Nuts with a nominal diameter between ¼ and 2½ inches are covered in this specification.