2a all ends thread class 2a 1st end thread quantity per inch special o-ring material, per mil-p-5510c, do not dupe to any other nsn zinc or cadmium or phosphate surface treated un 1st end thread series
2a all ends thread class 16 1st end thread quantity per inch special o-ring material, per mil-p-5510c, do not dupe to any other nsn un 1st end thread series
2a all ends thread class 16 all ends thread quantity per inch special o-ring material, per mil-p-5510c, do not dupe to any other nsn cadmium or zinc or phosphate surface treated un all ends thread series