Transmission parts are parts used with the part that has the role of transmitting power. There are those that transmit power directly by contacting the part that is generating power, and those that transmit power without contacting them, and there is also a difference in how power is transmitted. Transmission parts include couplings and shaft fittings, rotary shafts that connect the rotating shaft to pulleys and gears, timing belts and pulleys related to engine ignition, drive chains and sprockets, etc. Others include tensioners that apply tension to various belts, gears with teeth around them, non-contact transmission components that use magnetic force to transmit motion without contact, etc.