This technology can also be retrofit on existing gamma 3 systems. The gamma 4 cleaning head can be adjusted to give you 4 different flow rates. A & A 565642 Gamma 4 Low Flow Cleaning Head Internal - White FeaturesG4 is the most efficient and longest lasting pop up head that a&a has ever madeG4 body and spring are reinforced and heavy duty for longer lifeSpecificationsColor: WhiteWeight: 0. Adjusting the orifice size and does not require a tool.