This is a very unusual Air Manifold we have found in Sundance brand Hot Tubs nut can be found in others as well.. It is a 16-port manifold with (16) 3/8" barbs and 1-1/ 2" slip x 1-1/2"spigot or street meaning that a piece of 1 1/2" which measures about 1 7/8" Outside Diameter into the bell end and the spigot pr street end glues into a 1 1/2" fitting... You can glue these together for more outlets and you can also plug off barbs with this plug Barb Plug 3/8" Slip for Air Manifold and more Waterway ....
If you need other 1 1/2" fittings look here: https://spapartsnet.com/plumbing-and-related-parts/pvc-plumbing-fittings/1-pvc-fittings/
If you need 3/8" Fittings look here: https://spapartsnet.com/search-results?q=3%2F8%22%20barb
