Depending on what kind of project you are working on, you will want to buy a bit long enough to cut what want, but not necessarily much longer than that. Also, if you are going to use a pattern for the bearing to ride against, will you use it on the top or bottom of your work piece. That determines whether you want a top or bottom mounted bearing.
If you are routing small pieces (4-5 inches (100-125mm), you might wish to use a wood vise to hold the piece instead of your fingers. Much better to chew up the vise than your fingers. The picture will also give you an idea of what the Bearing does.
Last edited by DesertRatTom; 07-16-2015 at 11:07 AM.
Reason: add a sentence