Bearings are what allow the gears to rotate effortlessly. They are typically produced away from bronze or brass, they usually match into races (or grooves) during the gearbox housing. On the other hand, inner filters are dearer than externals and it is way harder to switch internal filters, as you’ll https://filtergearbox90987.blog5star.com/34581767/helping-the-others-realize-the-advantages-of-filter-gearbox