Waterway Whirlpool jet barrel diffuser - Snap In style. This is the white wine glass shaped plastic rear on the jet that often perishes with chemical abuse / mis-use.

It also has the locating lugs attached, which hold the jet barrel in the jet body. These lugs sometimes break off, requiring a replacement diffuser or jet barrel. 

Suits both Adjustable (as supplied) and Non-Adjustable ( after cutting the rear scoop off)  jet barrels in the Whirlpool snap-in style range. 

These diffusers are very tight and often can be difficult to fit. As a result we generally recommend replacement of the complete jet internal instead. Diffusers broken or damaged whilst trying to fit them are not covered by warranty.