The FORSÅ lamp from Ikea has only one option of attaching it to a heavy foot, which did not fit my desk. I bought only the TERTIAL lamp vise, which unfortunately has an installation hole that is too wide. All it took was a simple adapter and the FORSÅ lamp could be mounted on the TERTIAL lamp holder without any further problems.
Cylinder outer diameter: 13mm
Cylinder inner diameter: 8,2mm
Cylinder height: 30mm