These are very widely used by a number of spa manufacturers. These are available in a number of colors and styles.
Poly jets screw into the jet wall fitting with the very fine threads shown in this photo.
This jet has a directional nozzle.

Material
  • Plastic

Face Diameter
  • 3-1/2"

Length
  • 3-3/4"

Hole Size
  • 2-5/8" (For Wall Fitting) This is a part of the jet body and is not shown here.

Markings
  • "218-6010" is molded on back of the face