Question about CSL HDMI adapter, Full HD - extension - coupling, HDMI socket to HDMI socket

I did some googling. 3 out of 4 dealers say: Maximum resolution: 2560×1440 or UHD (1440p).
The other one says 4K support. The only one I found in 4K was:
Icy Box IB-CB005 HDMI Coupler (Dual Coupler).
At least on the manufacturer's site. But there's nothing about 60hz.