[QUOTE=oldred The Earthquake impact wrenches are a ripoff of the IR "Thundergun" but they did a good job copying it, the things are brutes and the 1/2" is a tough customer, at least mine has been. [/QUOTE]
We bought the 1" version of this wrench a while back and its seriously powerful. We were rebuilding one of the hoe cylinders on a Case backhoe. Had a 3/4 impact on the piston nut and a pipe wrench with a 10ft cheater on the socket. Wouldn't move. Checked the manual and the torque spec on the nut is 2300 ft-lbs. HF store is close, so we figured we'd pick up the wrench and just return it if it wouldn't bring the nut off. One good brrrrrp and the nut was off. I was impressed at how tight the wrench is overall, since the impact mechanism in even some real high dollar big impacts seems loose as a goose. We did drop off the quick coupler at the air drop where we were working and hook a 3/4 hose straight into the 1/2" ball valve on the line since no standard size coupler will pass the air a big wrench needs. Even so, the air consumption was way less than I'd expected. That wrench is about $250. No idea what the $99 one inch one is like, but probably not so great.