See Aluminum Tolerances
Anodized Aluminum Round Tube 6063 Clear offers exceptional corrosion resistance, light weight, good formability, and slighly higher strength than 6063-T52, but half that of 6061. The anodized surface of this 6063 gives it a longer service life with minimal upkeep and maintainance, in addition to being visually attractive and non-toxic. 6063 anodized is typically used in applications where corrosion resistance and aesthetic are more important than strength, such as piping, furniture, architectural trim, and decorative applications.
Tube is designed to act as structural support, whereas Pipe is designed to carry liquid/gas/material from one place to another.