This five-piece set of Level-Loc Reducing Rings fits the Kreg Precision Router Table Insert Plate, as well as Precision Router Table Lift, allowing you to customize the size of the opening around the bit. The set includes rings with 3/4', 1 3/8', 1 5/8', and 2 1/8' (19mm, 35mm, 41mm, 54mm) openings, plus one 'blank' ring that you can use to create your own custom-sized or zero-clearance ring. The set comes with a molded storage tray that has slots to hold all five Level-Loc Reducing Rings, plus slots to hold the three rings that come with the Precision Router Table Insert Plate or Precision Router Table Lift. Each slot is marked with the opening size, making it easy to keep the rings organized.