This Center Ring, that is also supplied in the #QPK-101 Standard Shower Kit, is used under the drain riser and on top of the clamping flange bolt heads of the drain to hold the float sticks (1in. to1-3/4in. tapered x 36in. long) in a vertical position while introducing the dry pack mortar mix (4 parts clean sand /1 part Portland cement). Additional Center Rings are often needed to make use of "leftover" gained sticks.· Used with Standard float sticks to begin at the shower drain; keeps the drain risers adjustable for incoming tile thickness· No need to fill inside the ring with mortar· Has 24 slots for engaging the float stick end tabs, accommodating any shower shape· Non-rotting high impact plastic, holds float sticks securely. Material: Polystyrene.