Optimal HDMI cable length for 4K

Is a 5m 2.1 4/8k HDMI cable OK to use without getting any signal loss or degradation?

It may be my imagination, but the quality of 4k directly from my TV appears to be slightly better than the quality from the 360 box.


I've looked through the internet but there are too many conflicting opinions of what the maximum length for a HDMI 2.1 cable should be.

Thanks.