Polyolefin Heat shrink tubing can be used in a variety of applications in the military, commercial, and consumer markets. All heat shrink tubing will shrink lengthwise as well as its diameter; 2:1 shrink tubing will shrink one half of its nominal diameter and less than 7% of its length. The diameter of heat shrink tubing is measured as a round tube, not flat, so make sure that the shrink tubing is larger than what you are covering.