Size Chart was very helpful and accurate. I ordered the small size for my ST205/75R14 trailer tires and they fit perfectly. These cases feel extremely durable due to the thickness and material. I love how easy they were to use with a rubber band instead of using a string behind the bar to attach them. Ordering a size small provided a snug (but easily removable) fit. I'll update the post later when I see how long lived they are in California's Central Valley lol.