One-Piece molded design resists abuse. All round-end tanks have an extra heavy duty, molded rim and an extra-deep sidewall rib design for additional strength. Round Tanks have a formed open rim. New heavy duty, molded-in aluminum drain fitting and 1-1/4 poly drain plug ensures a longer life. (PRE214 & PRE216 have no drain plugs because they are easy to tip.) FDA food-grade approved poly, tested to -20F, corrosion-free, impact resistant and recyclable. UV protected.