Precautions:
Casing diameter: generally called the flattened width, which is half of the circumference. Therefore, you must first calculate the circumference of the product before buying it, and then divide it by 2 to get the required sleeve width.Usually, you can buy a larger 5-10 mm to fit the battery. The shrinkage rate of the heat-shrinkable tube is about 48%. It doesn't matter if you buy a larger one. It won't work.
The circumference of the cylinder = diameter x 3.14;
For example, if the diameter is 20mm, the circumference is: 20X3.14=62.8mm;
The circumference of the cuboid = (length + width) X2
For example, if the length of the product is 95mm and the width is 25mm, the circumference is: (95+25)X2=240mm