The difference comes down to how hollow cylinders are measured or specified, and how they are measured or specified is dependent on what they are used for. The answer comes down to the manufacturing processes and where you want the natural process variation to be located within those processes. You can have either a consistent bore or a consistent outside diameter, but not both at the same time. At the very least, not with high precision.

Extrusion is used to manufacture the majority of smaller bore metal pipe and seamless aluminium tube. That is the process in which a billet of material is squeezed through a die to produce a long length of material with a uniform cross-sectional shape. . It works best with ductile materials, which is why aluminum is extruded in such large quantities.

Extruding pipe or tube entails forcing metal around a mandrel, which creates the internal passageway in the finished product. The wall thickness of the internal bore varies because, in practice, it is difficult to keep the internal bore concentric with the outside diameter. The manufacturer has control over either the bore or the outside diameter, but not both.

After extrusion (or, in some cases, instead of extrusion), some seamless aluminium tubing will be drawn in order to thin it down and improve dimensional consistency. Drawn material passes through a die and over a mandrel in a manner similar to extruded material, with the difference being that it is pulled rather than pushed through the die.

Extruded round pipe has a variety of uses.
One of the most common applications is in heat exchangers. This is due to the fact that aluminum has excellent thermal conductivity and is easy to weld. Because of its light weight, it is also in high demand for solar water heating systems that do not place an undue burden on a roof.

Extruded tube has a variety of uses.
In architectural and structural applications, extruded aluminum tube can be found in a variety of configurations. Handrails, support columns, and gate and fence posts are all examples of structural elements. It's also found in trailers and other transportation applications where weight is a consideration, and it's even found in electrical bus conductors.

Aluminum Tubes and Pipes are made of a variety of materials.
The majority of aluminum tube and pipe is extruded from 6061 or 6063 grade aluminum. This is due to the fact that they do not tend to work-harden, allowing the extrusion equipment to run more quickly. Despite the fact that 6061 is stronger, 6063 generally has a better appearance due to its finer grain structure, and it anodizes well when a colored finish is required.

Identical, but Not the Same
Pipe and aluminium seamless pipe are two words that refer to hollow cylinders, but as we've previously explained, they are not the same thing. Essentially, pipe makes use of the inside and tube makes use of the outside.