This kit features the updated style of vice bases for the larger line of GRS vices, one rubber and one plastic. The rubber base provides more surface friction, allowing the vice to stay stabilized and limits the amount of movement and tilt. The plastic base is a smoother, harder surface that is great for when you want to tilt and move the vice more freely within the base. These bases fit GRS Standard Block (#003-530), Low-Profile (#003-615), Satellite Vice (#003-784), MagnaBlock™ (#003-021), and Positioning Vice (#003-541).