Metal hollow bar tubing is hollow, structural, non-pressure rated tubing that is used for decorative and structural applications such as handrails, furniture, door and window framing, electrical components, heat sinks and musical instrumentation. It is characterized by its square, rectangular, or hexagonal shape. Construction types include extruded, seamless, welded or welded and drawn. Seamless withstands higher pressure because there is no seam or weld point. Welded construction has a weld or seam; welded and drawn is drawn over mandrel (DOM) to smooth the inner diameter. Extrusion construction creates tubing of a specified cross-sectional profile and shape. When selecting hollow bar tubing, there are several characteristics to consider such as material type, shape, wall thickness, width, and height.

Hollow bar tubing comes in a variety of materials which are selected for compatibility with fittings and environment. Hollow tubing is commonly made with various grades of aluminum or stainless steel. Aluminum is lightweight, has good strength, is weldable, and resists cracking and corrosion. Stainless steel is strong and corrosion-, and scale-resistant. Bronze and brass materials are also commonly used.

Wall thickness of hollow tubing refers to the thickness of the tubing wall, which is measured in inches.

Width refers to the exterior dimension of square, rectangular or hexagonal hollow tubing, and is expressed in inches. Square and rectangular tubing width is a measurement of the size of the hollow tube from outside edge to outside edge. Hexagonal tubing width is taken from an exterior flat-to-flat measurement. Hollow tubing height is measured in actual measurement, from end-to-end, in inches.