I was interested in these for a while until I found a 1/2" version cheap and bought it. It's advertised as breaking loose up to 500 ft lbs. I threw it in the back of my truck and thought it would be good for lug nuts. I tried it a few times and it would never bust anything loose, I always ended up grabbing a breaker bar or air impact. I even tried it on smaller 3/8" drive sized fasteners and I was not impressed. Not sure if I just got a bunk one or I just needed the 3/4" size to really do anything. I believe they make up to a 1.5" drive version also, but those larger ones are way out of my price range. To put it in perspective I bought a 3/4" IR impact for $40 used and a 1" armstrong ratchet/breaker bar combo set for $60, they keep breaking the bolts loose no prob. I sold the swench.
In other words, the specs are a bit inflated in my opinion.