Bearings are what allow the gears to rotate easily. They are typically made from bronze or brass, and they match into races (or grooves) inside the gearbox housing. Synchro rings have enamel on them that mesh Using the enamel about the gears, and they even have friction products on them https://laneovwyy.ampedpages.com/not-known-facts-about-filter-gearbox-61046503