Pipe and Tube | <p>In some instances the terms may be used interchangeably, however, there is one key difference between tube and pipe, particularly in how the material is ordered and toleranced. Tubing is used in structural applications so the outside diameter becomes the important dimension. Tubes are often put into applications such as medical devices that require precise outside diameters. The outside diameter is important since it will indicate how much it can hold as a stability factor. Whereas pipes are normally used to transport gasses or liquids making it important to know the capacity. Knowing how much can flow through the pipe is key. The circular shape of the pipe makes it efficient when handling pressure from the liquid flowing through.</p>