I don't know why you decided that you need heat shrink tubing, and I won't question it. But, in case you were interested to know, or are still trying to figure out why, these are the common uses, according to RS Electronics:
* Seal water and dust out of cable splices.
* Insulate cables and wires against extreme heat in aircraft, boats, and military vehicles.
* Provide a barrier between cable and corrosive chemicals.
* Color code cables for easy identification.
* Harness multiple wires together.
* Make longcord'>network patch cords.
* Neatly terminate the ends of braided sleeving.
* Improve the look of cables in motorcycles.
Size Matters
If you've fallen into an unexpected nap from reading the above, shake it off.
* Think about the ID of the tubing; it is going to shrink to about 70% of that diameter. For example: 1 in ID = 3/4 in diameter of whatever needs to be covered