You take out the bolt foot on your chrome wire shelving and replace it with a screw in caster. If you take 2 sets it is $40 for 8 casters.
1 set is $22.
I bought them for a storage project and didn't need them after all. I could not return them as the Amazon return window had passed.
If you are short on space, you can double stack shelving in front of each other to fit more storage in, then pull the front shelving unit out to get at the rear shelving unit. If you already have lots of storage space, you can pull shelving out to clean under and behind them.
Each set of 4 wheels has 2 locking wheels with brakes and 2 wheels without brakes. Caster screw is standard 1/4 x 20 inch used on most chrome wire shelving. You check out what you have before buying them.