Stacking a dado to get a perfect groove size requires shims. Most of us have used tape, paper, brass sheet, and other approximate systems that take a lot of fiddling around, including pulling off and replacing cutting blades and chippers. This set of shims makes all of this unnecessary. These shims are not only accurate, but they are slotted so that they can be slipped onto an arbor between blades with tweezers; you no longer have to pull the whole dado set off to re-stack it. They are color coded by thickness, so no measuring is needed. The set of 14 shims includes four each of 0.020" (.5mm), 0.010" (.25mm) and 0.002" (.050mm) sizes, as well as two 0.005" (.120mm) shims. Made from accurately thicknessed plastic that is oil and grease resistant, they withstand high torques and will not swell or distort. Arbor size is 5/8".