Looks great on my Keychron Q5 (1800 with a knob) w Gateron G Pro Brown switches. Unfortunately, Keychron Q5 1800 has a slightly smaller alt, fn and ctrl keys and larger + key on the right side so had to use the original Keychron keycaps for those keys. So anyone planning to buy Red Samurai keycaps for Keychron Q5 1800, buy the base kit w extra nishi and novelties instead - costs more but then you don't have any missing keycaps.
When I first saw these keycaps I knew I wanted to use them in a build, but had no boards I wanted to put them in. Recently I purchased a red neo 80 with the intent of buying and putting these keycaps on it, and the final result was completely worth it. The keycaps feel great and look amazing. I could not be happier with the build and will probably end up grabbing the blue variant to put in another build at some point.