In every synchromesh or dual-clutch transmission, there are gears with a synchronizer mechanism: They transmit the torque of the engine to the drive axle via a coupling body (synchro body) and a shift sleeve. There is one gear for each step of the transmission, meaning that a seven-gear transmission requires 7 + 1 gears.
A design that has proven successful is that of a wheel and synchro body, with the two separate parts joined and welded together.