This part is a Air Manifold, 3/8" Barb, 6 Port, Flow Thru, 1/2" Slip on both ends..The outside of each end could be considered 3/4" Spigot but it is really a tight fit..
You are buying on a 1" Street X (4) 3/4" Barbs manifold. The Manifold recieves a 1" pipe on the slip side which would measure about 1 1/4" inside Diameter and...