One size isn't actually one size. This is extremely important as you're trying to figure out the biggest tire you can fit on your 4x4 without ripping fenders off when you hit a pothole. Every tire nameplate has an actual size that is different than what the sidewall designation claims. A 35-inch-tall tire might actually be 34 inches tall from one manufacturer, 34.5 inches from another and 35.2 inches for a third. You simply have to look in the catalog or online to view the actual dimensions of the tire you are considering.