These are DFARS compliant custom A286 stainless steel castle nuts manufactured domestically in the USA for our aerospace customer.  They incorporate 7/16-26 2A thread and internal diameter of .328 +/- .005".  The cross slots measure .090 +/-.005" and unthreaded shoulders both measuring .394"+0.000/-.004 in diameter by .063" +/-.01.  Full certs including a FAIR are required as a part of the deliverable package.