The original metal “jaws” my Panavise came with are not properly straight, so the vise would always be closed at the bottom and open at the top.

Also the rubber that goes over the metal paddles is not really suited for properly gripping thin material like pcbs and the like.

These jaws have horizontal and vertical grooves allowing me to grip thin and reasonably small round material properly without it slipping out all the time.

Depending on the tolerances of the two “sliders" that the jaws bolt to you may need to add small shims on the outside to account for slack between the sliders and their rails - mine are shimmed with four layers of paper, approximately 0.3mm.