Australian Spa Parts - Waterway Plastics Dual-Flo, Quad-Flo, Turbo Diverter & Power series spa jets

Waterway Dual-Flo and Quad-Flo Diverter Jets and Power series spa jets. 
Popular in the 1990's on many Australian and other spas.
Dual-Flo diverter jets have been used heavily on Maax Spas up to approx 2010
Quad-Flo diverter jets have been used on numerous brands until around 2003
Power series jets were used on Hibiscus Spas in the 90's

Power series jets have a shorter barrel/body than the diverter jets.
The only difference in function between a Dual-Flo diverter and a Quad-Flo diverter is the position and amount of rotation of the jet barrel.
The threaded retainer ring dictates which type it is. Reversal of the retainer ring is required on some installations to make the jet work correctly. 

Turbo Jets are relatively new since approx 2012 and are a replacement option to dual / quad flo jets as well as other diverter jets.