Which Bearings Should I Choose?

Metal side bearings have sides which are attached to the outer race and come very close to the inner race but do not touch it. Metal side bearings have a slightly lower rolling resistance than rubber side bearings do with the tradeoff being that dust and moisture can enter the inside of the bearing which may cause it to fail earlier than rubber side bearings.

Rubber side bearings have sides which are attached to the outer race and gently touch the inner race creating a seal that prevents dust and moisture from entering the inside of the bearing. Rubber side bearings have slightly higher rolling resistance than metal side bearings do with the tradeoff being that they may last longer than metal side bearings.