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
Barb Adapter 3/4" Barb x 1/2" Spigot , The Glue Side glues inside a 1/2" Fitting which would measure 3/4" and a 3/4" ID tube would be glued over the barb.