A nice 6" vise you got there Bruce!
I think earlier I advised you to not get any bigger than a 4" vise, but that was before you decided to buy a big knee mill with a table that needs a big six incher!!
The key issues to look for on a vise like that are checking that the vise ways are fully parallel with your table, and that your movable jaw doesn't "jump" up any measurable amount when you clamp onto a work piece!!!