I own a set with the old Corningware cornflower blue pattern on the sides of the pieces. Very sturdy kitchenware. Can go from fridge to oven to table.
Sorry, you sure can use them in the microwave or the oven, but not stovetop. They are not skillets other than the shape.
Excellent for reheating leftovers. These are pieces designed to be purposely shallow instead of the casserole-type cookware of the square or deep round traditional Corningware.
But it is actually glass and will fail if direct heat is applied by putting the skillet on a burner. Just think of it as a different shape from Corning, but the same as their other store or heat type vessels. It's not a skillet in the sense that it is used on a burner with direct heat. There is no way I'd put mine on a stovetop or burner. I tried it with the smallest one of the set I own, with a low flame, and it cracked. Lesson learned.
I have mine for a very long time and they don't chip or crack or even show any scratches. I put them in the dishwasher and stack them in a cupboard without a second thought. They are really useful.