Can you provide an explanation of bike tube sizes and how they are determined?

Bike tube sizes are determined by the diameter and width of the tire they are meant to fit. The size is usually printed on the side of the tire and will look something like "700x25c" or "26x2.1". The first number refers to the diameter of the tire in millimeters, while the second number indicates the width of the tire. When choosing a bike tube, make sure it matches the size of your tire to ensure a proper fit.