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A little different though useful in some of the same situations is heat-shrink sleeving. This comes in various diameters and shrinks to half the diameter when heated. Slipping a piece over a wire join is much better than using PVC tape. You can shrink it (ideally) with a hot air gun, or if you don't have one to hand, holding it very close over the barrel of a soldering iron will do it, but you need to be careful not to let it touch.