Anti-friction bearings and bearing systems, as follows, and components therefore: Note : This category does not apply to balls with tolerances specified by the manufacturer in accordance with ISO 3290 as grade 5 or worse. (a) Ball bearings and solid roller bearings, having all tolerances specified by the manufacturer in accordance with ISO 492 Tolerance Class 4 (or national equivalents) or better, and having both ‘rings’ and ‘rolling elements’, made from monel or beryllium; Technical notes: 1. ‘Ring’ —annular part of a radial rolling bearing incorporating one or more raceways (ISO 5593:1997). 2. ‘Rolling element’ —ball or roller which rolls between raceways (ISO 5593:1997). (b) Active magnetic bearing systems using any of the following: 1. Materials with flux densities of 2,0 T or greater and yield strengths greater than 414 MPa; 2. All-electromagnetic three-dimensional homopolar bias designs for actuators; or 3. High-temperature (450 K (177 °C) and above) position sensors.