Copper tubing, also called copper pipe, is commonly used in plumbing, heating, cooling, and other systems. Lightweight copper is antimicrobial, durable, and more resistant to corrosion than other metals. Types K, L, M, and DWV (Drain, Waste, Vent) are designated by ASTM International standard sizes. Each type represents a series of sizes with different wall thicknesses. Copper tubing must be permanently marked in accordance with its governing specifications to show tube type, the name or trademark of the manufacturer, and the country of origin.