I have one and it works good for removing lug nuts. I have had it for 10 years and have never had a problem removing any. I keep it in the trunk just in case I need it. How it gets its impact is it spins a weight and when it reaches a certain speed it locks onto the shaft and hammers the socket like a air impact wrench. It is definitely slower than a air impact wrench, but faster and easier to use than a lug wrench.
Cancer's a bitch! Enjoy life while you can! LIVE, LOVE, DRIVE...CAMARO!
Previous Camaros: 1974, 1979 and 2010.