To ensure that you will make the right decision, it's important to consider the construction of a ball bearing, and how it influences the overall performance of the device. Familiarize yourself with sealed and non-sealed bearings, so that you know which is best for any given situation.
Non Sealed/Open Bearings
They are the easiest to find; however, this design has nothing that protects its moving parts.
This type has a seal around the moving parts, which is usually made from rubber or metal.
It is more difficult to clean a sealed bearing, but it has to be done less frequently than with an open bearing.
A sealed bearing is self-enclosed; not only does the seal lock out debris, but it also keeps lubrication trapped inside. Open face bearings require a lot more maintenance if they are going to last a long time.
While a sealed bearing may endure, an open face bearing experiences the least friction when clean, providing superior speed at the cost of vulnerability.