Swivel chair casters sometimes break easily, but replacement casters are available at most hardware stores and home improvement centers.
Step 1 - Purchase the Correct Size
If one of the old casters has fallen out or broken off, use this to determine the size you will need for replacement. Also make note of how many casters are on the chair because you may need to replace them all for the chair to sit evenly on the floor. Take the caster to the store with you for comparison.
If you need to remove a caster to measure, lay the chair on its side and use the pliers to grip the base of the caster that goes into the chair leg. Turn it to the right to unscrew or dislodge it, and the entire piece should fall out. Some have a screw that you may need to loosen for them to fall out.
Step 2 - Install the New Swivel Chair Casters
Most casters have instructions on the back of the package. Basic installation is simply pushing the caster into the opening on the bottom of the chair leg and tightening it down. If it has screw adjustment, adjust appropriately.