Herman Miller EA108 bases accept either casters or glides. Sometimes bushings or inserts are required depending on diameter of the recesses in the legs vs. posts on casters. I am not sure if this is also the case with Vitra production, but it should be an easy changeover if you have the correct parts. Perhaps Vitra or Graham Mancha can advise, but it's important to remember that it is a fixed-height chair and adding casters will raise the seat height.
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