3:1 SHRINK RATIO - Electrical heat shrink tubing 1/2 inch is made of polyolefin with a meltable adhesive inner layer that can withstand temperatures from -50 to 125 degrees Celsius. Wire shrink wrap tubing shrinks to one-third of its original size when heated and is more resistant to stretching and vibration and marine grade heat shrink tubing has a higher tensile strength than regular heat shrink tubing.