[QUOTE=Gary Slusser;376788]I found those that didn't have an internal flow control to be a bit less quality and usually the class B lights. In my other post I led people to believe that the strength is either 16 or 32,000 and I should have added most class As go to 40,000.

I use Trojan, which is arguable the best, and they don't have flow controls....what brands come with flow controls???? Even the one you sell on your own website says you include an external brass flow control.

Isn't the dosage...which is the correct terminology, a function of the "contact" time in the chamber? which is function of the flow rate... So, the same unit can be rated for 16,000, 32,000 or 40,000 depending on how fast you run the water through it.