Joe, i'm not trying to burn you here or anything, this is just to highlight the over all opinion of everyone here so you don't waste your 20 bills.  Look up the umpteen posts made about those dumb things in the last month or so and you'll see that they are a BIG WASTE OF TIME AND MONEY.  Nothing more than an inline resistor that "fools" your motor into thinking its supposed to run harder than it has to.  Even if it did work the way they claim it does, I personally don't think they'd do anything anyhow.  Lots of other things you can do to your Zuk for around $20, with a ton more benefit.  Happy Muddin' , man.