The Mazzei Red #684K Ozone Injector is used on hot tubs with tiny, low flow circulation pumps.
3/4 Inch - Hose Barb Connections.
The Red Injector works great on small circulation pumps like the Waterway Tiny Might and Laing Circulation pumps.
If you have a larger circulation pump or 2-speed pump, use the #884K White Injector.
Mazzei Brand Injectors are Highly Recommended.