I'm on my second set of Continental Gatorskins (700x23) in 6 years. In the 6 years I've been running them, I've only had one flat (ran over a piece of wood with a staple sticking straight up). I ride all kinds of surfaces, including gravel, blacktop, concrete, asphalt, etc. The Gatorskins last a long time, are nearly puncture proof, and offer good rolling resistance (they're not meant to be a race tire, but I've done some triathlons with them and passed a lot of people with racing tires ).