The full power 400 w/s Power Pack with X-tra Fast 2.5 second recycling time is made to be used with the Quantum X series Heads or any of Lumedyne's Heads used with an Auto Module for power control. The Quantamatic Packs have an On/Off switch and a Battery Gauge, that's it. There is no power level switch to accidentally have in the wrong power setting. Fewer parts make the Pack slightly less expensive than a similar Pack with power control, but it also has fewer components that could possibly fail or malfunction.