When I added casters to the bottom of a stand of drawers I went to Home Depot and got caster wheels that they sold. Unfortunately They were only rated at 50 pounds. I had to change them to a caster that was rated at 220 pounds, which I found at www.Amazon.com for $8.40 each made by Steelex company. They also have a double locking ability to allow me to lock them in position.
This new wheel allows me to roll my stand and other mobile bases easily over my concrete floors unlike the original wheels that were under-rated. I think a 3 inch wheel diameter is the minimum wheel size you should use.