These things have form for simply not working. They are very fussy, and need constant, skilled tuning, plus they have form for shabby build quality meaning mucho leaks. I don't know why you're either considering buying one, they have terrible reviews and scare stories splattered all over the internet.
Even a prism would be better. FWIW accept the pain and buy a remora - 90% work very well, easy to tune, great follow up and rep. Te skimmer is an important piece of kit so buying abject junk is a false economy.