Conti GP 4k's are great. YMMV. I just put on a 25 rear (vs. 23 up front) cause I ride a lot of crappy surfaces. I have Sp. Armadillos on my MTB. Three years, one NAIL puncture. Could have ridden it for many miles with the nail embedded, I but made the mistake of removing it 10 miles from home. Instant flat. It was doing fine til then. I got some unpleasant pinch flats with Conti Gatorskins in less than 30 miles. Maybe it was the rim's fault. (My fault mounting? Maybe, but it never happened before or afterwards with Vittorias, Specs, Conti 4ks, Panaracers.)

Anyway the 4ks are very nice puncture-resistant very good handling tires.