Aluminum flagpoles can be rigged with either an external or internal halyard system.
External systems have the rope and other rigging on the outside of the pole. This is a tried and true system, but prone to vandalism and sometimes noisy when the wind blows.
Internal systems keep the equipment on the inside where it is safe and quiet; the halyard is accessed through a hatch near the base of the pole. This is a more expensive option.
Aluminum flagpoles that are inground must be firmly rooted in a groundsleeve and concrete foundation to stay aloft. Be sure that at least ten percent of the pole’s length is underground, and that your flag is no longer than forty percent of the pole height.
If you buy a telescoping aluminum flagpole, be sure that the sections lock into place, rather than just wedge together. This will ensure stability in the event of high winds.