Betterley Tru-Cut Blade Insert System. Fits Powermatic Model 66 Patented design is precision engineered to maximize the performance of your table saw and blades Machined flat aluminum, mirrors table surface completely to blade, giving unparalleled support Leveling system insures accuracy, spring-loaded side plungers position insert, prevents vibration Significantly increases safety and decreases kickback, pre-machined for factory splitter/guard Kerf inserts are easily changed within the main insert, allows one insert to be used with all blades