Marquis Spa Wave Jet HK16 Twin Spin Stainless 4 1/4 Inch 320-6748

Marquis Spa Wave Jet, Twin Spin, Stainless steel and gray color and style MRQ320-6748 or 320-6748.

Jet Face measures 4 1/4 inches across the front jet face diameter.

This jet is also part of the HK-16 HK16 jet family.

Also see the HK16 directional jet MRQ320-6747.

HK designations are old-style Marquis Spa nomenclature - they refer loosely to a family of jet types and are no longer used to identify specific jets. 
But the two jets (twin spin MRQ320-6748 and directional MRQ320-6747) are considered HK16 jets.