This is the most rugged poly tank on the market. It features a closed-lip design that is incredibly strong and won't buckle to crowding livestock. Each tank is made of FDA food-grade high density virgin polyethylene so tanks won't rust or corrode. This tank is resistant to feedlot acids and resistant to UV damage. Tanks have a screw-in drain plug and all tanks come standard in gray. 3/4" NPT drain plug insert included.