First time buyers of poly tubing often make a mistake in determining the size (width) needed for any given application. To avoid mistakes, measure the circumference of the largest point of the product to be inserted into the poly tubing, divide by two (2) and add one (1) to two (2) inches. The tubing must be larger than the product which will be inserted into it.
The most common mistake is that the diameter of a product is measured, then the width of the poly tubing is chosen by adding an inch or two to that diameter. Because poly tubing is measured and sold in its flat form, the width does not indicate the diameter of the tubing. It’s a very natural assumption that width=diameter when one is unfamiliar with the different methods of measurement.