Vimeo member Marthin Fort put this video together on how to adjust the bearings on the Konova Video Camera Slider [Thanks Marthin]. Over time, you may end up with a little play on your slider so to correct this you will need to get the top part of the carrier off, and then unlock the bearing underneath. Once the bearing is unlocked, adjustments are made by turning the bearing clockwise or counterclockwise until it fits well between the rails. The Konova Video Camera Sliders (found here) are available in a variety of different sizes, but generally the bearings can be adjusted in the same way.

Konova Video Camera Sliders