Waterway Plastics Classic/Econo Bath Jet Series Nozzles.
There are 4 Nozzles available. Each of these Nozzle sizes must match the jet body.

When deciding on the Jet Body and therefore the Orifice Nozzle, the Ideal standard would be 0.275 and this is available in Standard (X7) or Non Adjustable (A7).

The orifice is indicative of the pressure associated with the jet. A larger orifice, for instance A3, means more volume with less pressure. A smaller orifice, for instance A5, means less volume with more pressure.