My table was 2.5 cm, I think the clamp can take about twice that. But I had to return the product because my WLAN in the shop has 5GHz frequency and Enterprise encryption - so I can't measure it.
6cm. I have a USM table. It has a thickness of 7 cm. It doesn't work there. The Keylight is compatible with the additional Bosen plate (approx. 50 Fr.).