This is a as-568-14 item, per mfr;
A nonmetallic circular item with an aperature, having a solid round cross-section. They are used primarily for sealing. For items with other than round cross section, see packing,preformed. For noncircular items with a round cross-section, see seal,nonmetallic round section and rubber,round section.
Classification: Gaskets, washers and other seals, of vulcanized rubber other than hard rubber
NSN 6320-01-498-4954
NSN 5985-00-120-1273
NSN 7035-00-413-0992
NSN 5925-01-391-7718
NSN 6220-01-332-1395
NSN 6650-00-754-2276
NSN 6645-00-318-9412
NSN 5975-01-543-8693
NSN 5950-00-808-2570
NSN 5985-00-240-2899
NSN 6105-01-499-5923
NSN 5935-00-468-6074