Bearings are what allow the gears to rotate easily. They are usually built away from bronze or brass, and so they in good shape into races (or grooves) in the gearbox housing. Synchro rings have teeth on them that mesh with the tooth on the gears, and they also have https://filtergearbox87429.worldblogged.com/40147157/an-unbiased-view-of-filter-gearbox