This part is a Manifold that features (6) 3/8" Barbs and is Flow Thru, 1-1/2"slip x 1-1/2"spigot..
To plug the barbs you can use these plugs:
Barb Plug 3/8" Slip for Air Manifold
This part is a 10 Port Air Manifold that is 1-1/2" Slip x 1-1/2"Street with (10) 3/8" Slip Barbs.
The 1 1/2" Slip end accepts a pipe or fitting that would measure about 1 7/8" OD and the Street end...