Plastic-Coated Copper Tube is manufactured for use when copper tube is to be buried or used in a potentially aggressive environment. Some building and insulation materials may contain chemicals that are potentially corrosive to plain copper tube, requiring it to be protected to ensure its longevity in service. Our plastic-coated copper tube eliminates the need for on-site tape wrapping or sleeving, creating a savings on labor and ensuring a professional-looking installation. Important note: Plumbers historically refer to pipe and tube by its ID or inside diameter. For example the ridged ½" x 10' lengths of copper tube sold at Home Depot stores are ½" ID and 5/8" OD, outside diameter. However soft copper tube such as this, is not considered a plumbing item but an HVAC item. Heating, ventilation and air conditioning contractors refer to tube by its OD, outside diameter. So two parallel trades refer to the same size tube by two different sizes. This can result in frustration and mis-ordered product. To avoid this, when ordering soft copper make sure you double check the OD and ID that you need before ordering. If you open the PDF of the specification sheet you will find that this product has an OD of 3/8" and a "nominal size" or ID of 1/4".