35mm cylinder shim for monitor mount arm on 10-series extrusion

I recently bought a dual monitor arm, but I only wanted one arm on my main desk. The other arm should go on the workbench, which is framed with 10-series (25mm) 8020 aluminum extrusion.

So I needed a way to make the arm, which is designed for a 35mm-diameter post, clamp onto a 25mm square extrusion. This little jobbie does the trick! Print four, twist 'em, in, and proceed with the mounting.