The fastest rolling MTB tire I have tried. Even faster rolling that a Maxxis Aspen or RR. However, it takes some skill to get it to hook-up. On loose, it's the sketchiest tire I've ridden. If you are ridding anything technical, this tire requires considerable focus.
Sooo the Race King is fast, like you can feel its faster than Maxxis stock tires on 2021 Giant Anthem - period. BUT they don't have the tread for slop or loose stuff - you kind fly through it. If you need to change direction or grip hard - best to surf the slide. still fast is fast and I would take the speed over control or short track racing.
I use these tires on my bikepacking rig. They roll fast on hard pack and got a good grip when the terrain demands it. They are also very light at only 580gr while the Vittoria Mezcal 2.35 on my MTB weighs 730 gr, that 150gr difference is significant when weight counts.