Plant extracts

A pipe is a tube or hollow cylinder used to convey materials or as a structural component. The terms pipe and tube are almost interchangeable. A pipe is generally specified by the internal diameter (ID) whereas a tube is usually defined by the outside diameter (OD) but may be specified by any combination of dimensions (OD, ID, wall thickness). A tube is often made to custom sizes and may often have more specific sizes and tolerances than pipe. Also, the term tubing can be applied to non-cylindrical shapes (i.e. square tubing). The term tube is more widely used in the United States, whereas pipe is more common elsewhere in the world. Both pipe and tube imply a level of rigidity and permanence, whereas a hose is usually portable and flexible. Pipe may be specified by standard pipe size designations, such as nominal pipe size (in the United States), or by nominal, outside, or inside diameter and wall thickness. Many industrial and government standards exist for the production of pipe and tubing.