I purchased a pair of Schwalbe Stelvios for my Cannondale back in June of this year. I have experienced a couple of sidewall punctures, a couple of tube valve failures - but, this week, I had a piece of glass the size of the tip of a nail that penetrated the "tread" area of the tire. These are supposed to offer puncture protection owing to the Kevlar in the area of the tire that contacts the road. This piece of glass was what you might expect to see if a car windshield shattered - not a big, sharp, dagger sized slab, just a bit of glass a little larger than a grain of sand.
It obviously lodged in my tire and worked its way through. I thought that would not happen with these tires.
I am now an expert at patching tubes and have developed a nice collection. I am half tempted to go back to my Armadillos. I never experienced a puncture flat using them.