All Wright Standers have rear wheels that help prevent rollover in certain situations. It is important to keep enough weight on the drive tires to remain in control of the machine. It is also important to manage what happens as the machine gets close to its rearward tipping point. When looking for a stand-on mower, be sure it has a feature that helps prevent the machine from passing its tipping point, resulting in an accident. Many other mowers brands do not have this feature. This feature is not patented and we recommend it for all manufacturers.