[Al Skierkiewicz]

Sanddrag,
It depends on what you plan on using it for. Outside, in the elements, those tolerances will quickly close down and you won't be able to pull stuff apart. It also will depend on what you use to cut the tubing to length. A hacksaw or tubing cutter will distort the cut end where a cutoff saw might not. A slight bend in the tubing will also close down the tolerance and since this pipe is not handled with care in hardware stores, expect a few dings here and there.
The ARRL Radio Amateurs Handbook has a table on aluminum tubing standard sizes for 6061-T6 tubing and good discussion on telescoping tubing sections for antennas. The current book should be on your library shelf. The table is in the chapter on antenna projects and will also show methods of joining sections and calculations for sag, overlap and windload if you need that info.