This little caster is quite the dynamo.  The original design for the S series was for heavy office equipment.  This caster was original equipment for some of the heaviest and largest copiers produced.   The wheel will not flatten out even after extended periods under maximum load.  The swivel raceway is heat treated and very sturdily constructed.  Use this caster for heavy loads that require a low overall height.  Excellent also for heavy applications that may have to sit long periods of time in one place.   The wheel will not mark floors.