When I tried this trailer diameter tool from Open ROAD Brands, i was blown away by how easy it made determining my trailers size.The durable construction and clear markings made it a breeze to use. It's a must-have for any automotive enthusiast who tows large loads. The only downside is that it's a bit pricey compared to similar products on the market. Nevertheless, if you're serious about making towing safe and simple, it's worth every penny..