Were do you purchase them because i am looking for 84mm ones.
With a vice, it is best to spend enough money to get one that doesn't flex and stays square and true. The cheap Chinese ones I have been around were not worth scrap metal price because the screw handle didn't turn true and the jaws would move and never line up properly. You also want a good base or table to bolt your vice too as things get exponentially worse with unplanned movement.