Trailer Hitch Receiver Sizes
To determine the size of your trailer hitch, simply measure the width and height of its opening. The two most common sizes of trailer hitch openings are 1-1/4" x 1-1/4" and 2" x 2".
2" x 2" Class III and Class IV Hitches
The 2" x 2" trailer hitch size is the most common. This is found on pickups, SUVs and even some full size sedans. Trucks and SUVs that come factory equipped with a trailer hitch will normally have 2" x 2" sized hitch. A couple of the exceptions are the 6 cylinder Ford Explorer/Mercury Mountaineer, and the Ford Escape/Mazda Tribute.
Curt, Draw-Tite, Hidden Hitch, Reese and Valley hitches with the 2" x 2" size fit into the Class III and Class IV hitch categories with weight capacities ranging from 3,500 to 12,000 lbs. On some vehicles Curt Manufacturing also offers Class 2.5 hitches with the 2" square opening.
1-1/4" x 1-1/4" Class I and Class II Hitches
Class I and Class II trailer hitches typically have the 1-1/4" x 1-1/4" receiver opening size. Class I trailer hitches are rated for 2,000 lbs. with a 200 lb. tongue weight capacity while Class II hitches are rated for 3,500 lbs. with 300 or 350 lbs. of tongue weight capability. These two hitch sizes are found most often on cars and smaller SUVs. There are a few Class II hitches that have 2" x 2" receiver openings, but this is not common.
You would think that any hitch accessory with an 1-1/4" x 1-1/4" shank would work in either a Class I or Class II trailer hitch, but this is not the case. Many hitch accessories are designed to maximize the weight capacities of the different trailer hitches. To keep a user from overloading a Class I hitch, Class II hitch accessories, such as drawbars and several bike racks and cargo carriers, are designed to not fit. Manufacturers accomplish this by placing a stopper in the back of a Class I hitch receiver so the drawbar or hitch accessory shank can only slide into the trailer hitch opening so far. On hitch accessories designed for Class II trailer hitches, the shank that slides into the hitch opening is longer. When this longer shank is slid into a Class I hitch, it will hit the stopper and the pin hole on the hitch will not line up with the pin hole on the class II accessory.
Class I hitch accessories will work in Class II trailer hitches. All of the decorative hitch covers listed for the 1-1/4" hitch size will work in both Class I and Class II trailer hitches.
Other Size Trailer Hitches
The third most common size trailer hitch has a 2-1/2" x 2-1/2" square opening. This size is only available for Heavy Duty pickups that can tow at least 14,000 lbs. Hitches with this size opening and weight rating are usually referred to as Class V hitches. Hitch accessories designed for 2" trailer hitches will work on Class V hitches with a 2-1/2" square opening with the use of a hitch adapter.
The least common hitch sizes are rectangular. Hidden Hitch and Reese no longer manufacturer these rectangular hitch sizes. They were Class I and Class II hitches designed for smaller cars. No hitch accessories are available to slide directly into a hitch with a rectangular opening, but bike racks are available that will mount to the ball hole on the hitch's drawbar.