Mules are slightly smaller than their horse parent, and when they grow they share traits of both a donkey (the long ears), and the horse (color, tail, etc.). A Mule in the grass.
For example, a 2014 Ford F-150 is considered a half ton truck but most variants can carry a lot more than 1,000 pounds in the bed. Since these terms are probably not going away any time soon, it's best just to think of them as smaller, mediumest, and more than medium.. (Pause for laughter).
The 150 is a lighter weight truck known as a 1/2 ton. The 250 is better suited for towing travel trailers and rated as a 3/4 ton truck. The 350 is a one ton truck that is usually the best for hauling big 5th wheel type trailers, but the 250 truck is highly capable too in this category.