Machine parts, namely, shaft seals being machine parts in the nature of mechanical seals, bearing housings for machines, headwheels being machine wheels, cable pulleys, single and double mechanical seals with gas or liquid lubrication for sealing liquid or gaseous media, cassette-type mechanical seals, mechanical seals with confining fluid seals, mechanical seals with a flushing function, mechanical seals with leakage recirculation, and mechanical seals with leakage control