Duo insulated steel bottles are a part of Milton's Thermosteel Range. They keep your beverages hot or cold for up to 24 hours, and feature a sturdy, leak-resist, screw-top cap. High-quality, corrosion-resistant steel bottle. Copper inner-coating for better temperature regulation. Keeps beverages hot or cold for hours. Simple threaded lid for easy use. 100% rust-resistant and leak proof construction.