This headphone holder mount on this lamp(https://www.amazon.it/gp/product/B09KL9KWXT/ref=ppx_yo_dt_b_asin_title_o06_s01?ie=UTF8&psc=1) or in any 9.5mm tube. The three hole at the back is for a M3 screw if it slide down. The top of my headphone mesure 24mm but if yours is different i left you the step.