Mfgr calls this a fuel pump seal; navair tm 19-40-523
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.
NSN 7035-00-703-3535
NSN 6650-00-684-3060
NSN 5996-01-165-9344
NSN 5999-01-216-4407
NSN 2925-00-113-6146
NSN 5930-00-960-7223
NSN 6110-01-145-3814
NSN 5965-00-104-3121
NSN 5835-01-274-1035
NSN 2925-01-170-8018
NSN 4140-01-419-5976
NSN 5935-01-115-0215