You will need to determine the thread size and pitch of your existing wheel nuts. This can usually be found in your motorhome's manual or by contacting the manufacturer. Once you have this information, you can then measure the diameter and length of the wheel nuts to ensure a proper fit. It's important to choose the correct size wheel nuts to ensure the safety and stability of your motorhome while on the road. Take the time to do your research and consult with professionals if needed, in order to find the perfect wheel nuts for your motorhome.