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 5990-00-716-7796
NSN 6620-01-158-5111
NSN 5915-01-153-7243
NSN 6240-00-617-1719
NSN 5945-01-388-1175
NSN 5999-01-605-4863
NSN 5985-00-937-4687
NSN 5998-00-488-4184
NSN 5905-01-200-7940
NSN 5950-00-872-6011
NSN 6220-01-246-4285
NSN 5975-01-411-6054