I purchased these for a set of training tires. They are specified by Continental to weigh in at 660 grams per tire. Both of mine weigh 770 grams a piece. They set up tubeless fine, and will work, but that is quite a bit of extra weight to push around. I also bought the 'Protection' series for my next race, and those weigh in at the specified 605 grams. I'm not sure how Continental missed this weight issue. I wrote Western Bike Works and they confirmed the 770 grams for the 'Performance' series tires. Bottom line These will be fine for training, but I wouldn't use them on race day.
I use the Race Kings on a Trek Superfly for mostly gravel riding. The tires are great for gravel work - not sure how they would hold up on a cross country MTB trail. I'm on my second set & no problems with the tires at all - no flats & plenty of miles ridden before they show any appreciable wear.
Swapped these onto a Trek DS for snow and trail riding. Great grip aired down a few PSI. Exceeds bike manufacturer width allowed but works perfectly. Great in the snow and mud.
I ride some basic local single track trails & dirt access roads. These tires are exactly what I needed to replace the road friendly tires on my dual sport. I now have adequate traction to climb hills without spinning the tires. If I don't have adequate traction, I probably need to dismount the bike anyway.