New in Box Ideal for house breaking your dog Grass Mat\Grid Tray\Base Tray The Base Tray holds the Grid Tray with the Grass Mat placed on to it. The urine goes through the Grass Mat and through the holes in the Grid Tray to the bottom Base Tray. The pegs on the surface of the Grid Tray and the raised platform of the Base Tray elevates the Grass Mat keeping it away from the urine. Grass measurements ~18" x 23"