Heat shrink tubing must be selected based on pre-shrink diameter plus shrink ratio for a proper final fit. Always measure the largest point (connector/crimp/splice). 4 mm+ are available, but shrink ratios (2:1 / 3:1 / 4:1). ink tubing it can be a bit confusing at first. Heat shrink has multiple different measurements that work hand-in-hand, and in this post, (and video), we want you understand what to look for to he when picking out a size for your ed to identify the size of heat shrink tubing. Selecting the wrong size can lead to loose fittings, poor insulation, or even damage.