How do you classify trailer hitches? Classes of hitch receivers range from class I-V 👍 Classes are determined by weight capacity ratings and tongue opening size 🙌 Class I and II have 1 and 1/4″ receiver opening and rate up to 3,500lbs towing capacity for small utility trailer, boats, campers. Class III has a 2″ receiver opening with tow ratings up to 6,000lbs for mid-size utility trailers and campers. Class IV has a 2″ opening and with a weight capacity of 10,000lbs for heavy boats and toy haulers, and are usually installed on heavy-duty pick-up trucks and SUV’s. Class V have a 2 and 1/4″ receiver opening with a weight capacity rating of 12,000lbs and are for hauling large boats, campers and anything your heart desires. 
You need to level your trailer. The trailer must be straight fore-and-aft in order to distribute the trailer’s weight properly. However, the receiver of your tow vehicle’s trailer hitch will not be the same height as your trailer tongue. To level your towing rig, we sell ball mounts made with different amounts of “drop” which is the distance from the top of the shank to the top of the ball platform which lowers the actual towing ball the amount needed (between 3/4″ and 8″). Most are reversible; turn the ball mount upside down to add “rise” if your trailer is higher than the car’s receiver. 
U-Haul offers so many trailers that it would seem difficult to find the perfect hitch size. This is not the case. All U-Haul trailers can be towed using either a 1-7/8″ or 2″ ball. This is the only way to get your U-Haul trailers towable using a 1-7/8” or 2″ ball. Thing you need Pay attention to your weight limit. Smaller options such as the 4×7 Utility Trailer only require a 2,000 pound rated hitchball. Auto Transport is their largest trailer and will need at least a 5kilo capacity hitchball. However, depending on what vehicle plus trailer it’s towing, a larger capacity may be required. So if your hitch ball is 1-7/8″ or 2″ and features a 5,000 pound weight capacity you can haul any cargo trailer U-Haul has to offer. To tow a car, your hitchball capacity must equal or exceed its total weight. Click here to find out how you can check your hitchball rating. Renada Penn, January 11, 2021. 
Additional material auto.howstuffworks.com This is why the dimensions of trailer balls can be used to classify them. You will need to know the dimensions of the unit: the distance from the centre of the balls, their diameters, shank lengths, shank widths, and the area between the shank and the ball. Most balls are two inches wide. However, heavy-duty industrial trailer ball can be as large as 2 1/4 inches. For a ball to fit, the hole of your ball mounting must not exceed 1/16″. To fit your ball, the shank must be at least 1/16″ longer than the platform that holds it. Lock the nut In place It will also be need to buy A ball that fits into your coupler. This was modified by Barbara Lee of Jundiai in Brazil, November 29, 2021.