A fitting in the form of the letter y with each branch usually fixed at 45 degrees (0.78539 radians) to the run. It has identical flanged ends.
NSN 4140-01-184-5648
NSN 6220-01-139-3520
NSN 6650-01-014-5990
NSN 6645-01-429-6768
NSN 5975-01-478-6847
NSN 5998-01-209-5819
NSN 5905-00-904-4412
NSN 5999-00-083-5591
NSN 5935-00-938-5394
NSN 4140-01-111-7416
NSN 2925-00-120-9302
NSN 5930-00-146-5148