Probably works great for anything 12mm and under. Maybe even some 14mm bolts.

For everything else, there is the Earthquake!

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=2623

Bwahahahahahaha!!!!

Ahem. :D

I have this one, and use it CONSTANTLY! The light weight makes these things a pleasure to use. By the way, $99 refurbished (http://bosch.cpotools.com/impact_drivers_-_wrenches/23609-rt.html) with a case, 2 batteries and charger.
http://bosch.cpotools.com/images/product/medium/23609-rt.jpg
This thing is still going strong, and still one of my most prized tools.

C

Though you wouldn't want to use HarborFreight's finest to tighten up valve cover bolts, or dashboard screws..... would you?

C

Lol, I just saw this...

Reminds me of when I first bought that damned thing, I used it for everything. I figured the "1" setting was low enough for things like water pump pulley bolts and clutch disk bolts.

Wrong! Snapped the 10mm water pump pulley bolt first impact and the clutch disk bolt on the 2nd... :D