This wall fitting is designed for concrete spas and includes an air intake for Venturi suction. It is usually used with an Eyeball jet, although different configurations are entirely possible.

For the Venturi system, you will need a length of 7 to 10 cm between the end of the injector and the nozzle. You can therefore cut the wall fitting to the desired length for optimal Venturi suction. 

You should plan on a flow rate of approximately 5 m³/hour for each jet of this type.

Dimensions
Length: 255 mm
Inside diameter of jet insertion: 40 mm
Inside diameter water inlet: 48 mm, for 1.5-inch hose
Inside diameter air inlet: 21 mm, for 1/2-inch hose
Outside diameter air inlet: 27 mm