Tubes are cylindrical, hollow, reinforced metal objects that are used to transport materials in a range of industries. The main parts of tubes are the outer diameter (OD), the inner diameter (ID), the wall size, the end type, and the surface finish. The OD is the external diameter of the tube, and the OD determines the size of the tubes. The ID is the internal diameter of the tube, and it affects how much material can flow through the tube. The wall size is the measurement between the two diameters, and it affects the amount of pressure and strength the tube can handle. The end type refers to how the tube is closed off, and this can be threaded, flanged, welded, or crimped. The surface finish refers to the quality of the surface, and this affects the quality of materials that can be moved through the tube.