An air caster is a device that can be used to lift heavy loads in a similar manner to a hovercraft, though usually only on surfaces that are both smooth and flat. typical air caster systems consist of several toroidal airbags and a compressor to pump them up. as they are pumped up, the airbags can create a positive seal to the ground if it is smooth enough. a thin cushion of air is eventually created between the caster device and the ground. this results in very little friction, which can allow heavy devices or may exist loads to be moved around without much effort. air casters can be integrated into various lifting separately. platforms can be constructed to lift virtually any amount of weight if enough compressed air is available. individual casters can also be placed under existing platforms, usually in sets of at least four. additional casters may be used to lift heavier loads, though four are typically required for stability. the main benefit associated with air casters is reduced friction. since the load is riding on a very thin cushion of air, a substantial reduction in friction can be obtained over traditional wheeled casters. in many circumstances, a single individual can safely move a load than the many workers that would have otherwise been needed. momentum can become a concern due to the lack of friction, so care typically must be taken when stopping very large loads.