The STAINLESS KING tumblers and mugs are crafted from durable, corrosion-resistant stainless steel to ensure superior performance and reliability. Completely rust-proof, each tumbler and mug features 2 layers of stainless steel for maximum heat and cold retention. Tested for optimal insulation and air-tightness, the STAINLESS KING tumblers and mugs are perfect for on-the-go hot and cold beverages.