Hello, I assume you mean the screws on the VESA mount? That depends on the monitor/screen to be mounted. I would say M6 or M8. Measure the length and buy them from a DIY store. Ask for pan head screws, for example. They have a large head for support. You may need to fit a spring washer underneath so that it doesn't come loose. Hope that helps.

I meant the screws that come with the arm. But thank you very much for your help.