WONDER Z-RING KIT 1 Heat Ring; 1 Honeycomb Firing Tray w 20 pins; 3 Fiber Free Tray Liners The radiant heat ring optimizes depth and vitality firing for layered buildups or lithium di silicate and large Yz (Yittra zirconia) restorations glazing regardless of where you place the units on the tray. They glaze perfectly. ADVANTAGES: Eliminates uneven temperature in firing zone; Optimizes the optical refraction (depth of shade vitality) of all layered ceramic applications; Adjustable ring accommodates larger cases. Eliminates cold zones on firing tray; Completely even heat across the tray surface; Eliminates dull glaze finishes (fire scale) caused by