Cage 34914 states they are the oem
A straight, one-piece fitting used to join two bosses or boss fittings. Both ends are the same size and have external machine threads (straignt threads other than pipe or hose series). It is designed to facilitate a gasket, preformed packing, washer, or the like to form a seal at the boss. The center section may be suitably shaped to accommodate a wrench.
NSN 6135-01-041-3829
NSN 5985-01-386-5898
NSN 5910-01-116-4420
NSN 5960-01-258-0814
NSN 5930-01-063-6559
NSN 6650-01-322-6431
NSN 6135-00-931-9049
NSN 5855-01-147-4785
NSN 5998-00-888-9887
NSN 6105-01-026-0165
NSN 6145-01-378-4321
NSN 6145-00-907-9399