I use 2 of them. One for rifles (pictured) and one for knives.
I drilled & tapped the holes in the vice & installed teflon pads & then put leather over them. The offset piece was made by Holzum (Jerry Crawford) and it works quite well. With the offset, I can tilt it up or down & swing it from side to side as well.
I suggest adding a 2x4 piece to the front of the bench so you can pull the vice out some to mount it. This makes it so you can put long items vertically in the vice, such as a barrel & not be obstructed by the workbench. I can hand a long barrel down & have the breech area at the vice to work in there if need be.
I bought two of them on sale at WoodCrafts for $ 39.95 each.
Keith Lisle