Rubbermaid Structural Foam Stock Tanks built tough for superior performance and long-lasting durability in all kinds of weather extremes. Seamless construction for outstanding durability. Oversize drain plug makes for easy drainage and cleaning of stock stank. 1-1/2" oversize drain. Stock tanks are great watering troughs helping to provide a better life for livestock. Optional all-plastic anti-siphon flat valve provides constant water level.