7 Mechanical seals, and their structural parts and fittings; mixers, agitators, reaction vessels, rubber, synthetic resin and other plastic machine parts for technical purposes, namely, steam traps, ball valves, condensation traps, butterfly valves, reducers, membrane valves, valves, vacuum filters, driers, coupling discs and brake linings, driving belts, conveyor belts, v-belts, and other clutch components, brake segments, injectors, cylinders, acid-proof fittings, and rollers all being parts of machines; O-rings made of metal for machines having rotating pump shafts and hydraulic cylinder pistons; O-rings made of metal for fluid and gas sealing apparatus; O-rings for machines having rotating pump shafts, pumps and valves; encapsulated O-rings for rotating pump shafts, pumps and valves; tube couplings for tubes and pipes, namely, non-metal pipe couplings and joints