3/8 by 1/4 in; hex shape
No other part numbers with same form, fit, and function found.
A fitting with pipe threads having a female connection inside of a male connection, used in conjunction with another fitting, to connect in the same line, two pipes of different sizes.
NSN 6130-01-585-5840
NSN 6145-01-538-4954
NSN 5930-01-016-0619
NSN 5905-01-207-2417
NSN 5975-01-005-8774
NSN 6130-00-621-2202
NSN 6645-00-216-6126
NSN 5855-01-616-6544
NSN 5998-01-434-8336
NSN 6650-01-272-9746
NSN 5965-00-918-3950
NSN 5910-01-555-7751