Well, according to the video on their website, the one that drops into the skimmer opening creates a vortex that will suck alot of air into your system, along with whatever floating debris there is. Basiclly what they have done is created the same effect as a lower water level by raising the height of the skimmer basket. Will it work, yes. Will it cause problems, most likely yes. You could just lower the water level and save $35 bucks.
What problem are you trying to solve with this device?