Nalgene® laboratory tanks feature a rim flange for strength and ease of handling. Tanks with 30-gallon capacity or less have a raised-center bottom for complete drainage. Tanks with 55-gallon capacity or more have a spoked bottom. High-density polyethylene (HDPE) tanks come with or without a needle-type polypropylene spigot. Spigot has 1-1/8"-12 female screw thread. Spigot is mounted on a welded polyethylene boss and accepts 5/8" ID tubing. Polypropylene (PP) tanks offer good stress-crack and chemical resistance. Maximum service temperature up to 104°C (220°F).