This is the smallest, lightest, easiest and least expensive way to add an f-stop to a 200 w/s power pack. Boosters only effect the highest setting on a power pack. Boosters require a power pack to run from a battery. Over 800 w/s through one head requires a 2400 w/s Quartz flashtube.
Stackable up to 2400 w/s.
Contains extra capacitors to increase the total watt/seconds available.
When you double the w/s you gain one f-stop (200 w/s to 400 w/s or 800 w/s to 1600 w/s) and get half as many flashes per charge.