The PanaVise 305 Low-Profile Vise Base is made for working closely to the bench surface. The Low-Profile Base accepts all 300 Series heads and any 0.625" (15.9 mm) diameter shaft. When used with the 304 Low-Profile Head it creates a very low-profile vise. It has a single control knob and exclusive "split-ball", which locks the head firmly in place. It can be secured by its three bolt circles, which are counter sunk and accept three 0.25" (6.3 mm) flat-head screws, which are not included.