The self watering trays are made from very strong plastic and comes with a fitted capillary mat. On the bottom of the tray are channels along which the water runs. The plants only take up as much water as they need. Large size - 55 x 65 cm. For more information on Bio Green Self Watering Trays and Automatic Watering call us and speak to one of our Watering specialists who will be happy to assist you in your purchase. Two of these products will fit inside the Jumbo Propagator