It's a 110mm clamping ajustable end wrench from stanly. I stole it from my little brother. You just twist it down like any other adjustable end wrench then clamp it kinda like a vice grip and it just hangs there so you're not fumbling with two wrenches.
My engine dollies are pretty low so I don't have to lift the car too much when pulling it. I rest the rear of the car on the dollies then attach the wrench to the bottom end of the bolt just sticking out under the side of the car. I use my ankle as a stop for the wrench (with thick work boots, that thing might kick and leave a bruise) then just reach into the engine compartment with the pneumatic. 10 seconds tops to pull the bolts.
Edit: Just looked it up, $18 at amazon:
Linkey to amazon