Rollers, which are the wheels, come in three standard sizes like one inch, two inches, and three inches. The face of the roller needs to be measured with a measuring tape for determining the required diameter of the roller. Rollers have been designed to operate within the tracks system; hence, the actual length of the rollers is less than the width of tracks. For example, a garage door roller of diameter 2 inches is required for a 2-inch track, but it has a diameter of 1¾ inches. The 1/4th fewer widths allow it to fit securely yet has the right amount of space for movement. Heavy commercial and industrial doors make use of the 3-inch track and hence, make use of 3-inch rollers. You should always purchase a roller size that the manufacturer recommends as that will perfectly fit your door.