We have one of these in the front receiver of the van. A vice is one of the most useful tools, and I wish we had it much earlier, probably would have saved my knuckles many times over when cutting something with the hack-saw or drilling while on the trail. Had considered bolting a regular vice down to a bumper, but never got around to it due to bulk and not finding one that fit well. This is fairly small, and uses the vehicle as the bulk.
The jaws have what is essentially sand embedded in the faces for gripping, but this mars what you clamp. I made some soft-jaws out of AL angle and machined some V grooves for holding rods (think motorcycle fork legs, or the like). It can rotate 90deg for holding items vertically.
I'm not a fan of the wrench/handle with all the advertising cut into it. Rather uncomfortable, but it works and it is handy.
-e