Give the valve box a lift with the stackable 13 X 20 in. Rectangular Standard Series Jumbo Valve Box Extension and Cover, or use alone to protect irrigation and sprinkler system components in shallow installations. The black riser is 6-1/2 in. high and adds 6 in. of height when added onto a 13 X 20 in. access box. The enclosure is built with reinforcing ribs for durability. The green overlapping cover is marked "IRRIGATION CONTROL VALVE" to identify contents inside the box. The irrigation valve box extension is made of polypropylene (PP) and the lid is made of high-density polyethylene (HDPE), both treated with UV inhibitors.