A typical scenario that calls for the use of SIMs is an uncooperative subject standing approximately 15-30 feet away in possession of a weapon, but without posing an immediate threat. The suspect is too much of a threat for "empty-hand" controls, and he is too far away for the use of a baton, pepper spray, or a taser. Since the 1960s American law enforcement agencies have experimented with and used SIMs as modified shotgun rounds and 37 mm rounds that had to be fired with special launchers. SIMs are used in situations in which deadly force is not justified, but the threat to officers and bystanders is sufficient to warrant incapacitating the subject from a distance. Since a variety of SIMs are available, the most important decision is what type of round to use in a given circumstance. Factors to consider are how much impact energy is required to incapacitate the subject and how accurate the shot must be in order to achieve the desired effect on the subject. A major factor that affects both accuracy and impact power is the weight of the munition. The size and mass of the subject is another major factor in determining the effectiveness of a SIM deployment. This article discusses the general features of SIMs and how their performance is affected by their characteristics. This is followed by descriptions of the following types of SIMs: 12-gauge square bean bags, 12-gauge tear-shaped bean bags, 37/40 mm bean bag rounds, 37/40 mm baton rounds, spin-stabilized foam baton rounds, and rubber balls or pellets. The circumstances under which each type of round is appropriate are described.