The Sig Bottle is molded with a 99.5% high purity quality aluminum plate with 600 tons of pressure. The body is completely seamless, lightweight and durable. The average wall thickness is 0.02 inches (0.65 mm) thin, and it retains heat and does not have cold retention. When disposing, please recycle it as an aluminum can. The interior is treated with a special coating that does not affect the flavor and is odor resistant. The cap is a simple and easy to use screw-on traveler cap. (NOTE) All sig bottles have a 15mm wide indentation at the bottom which is not normal in the manufacturing process.