Full grain, oil tanned cow leather with full grain leather lining.
Oil tanned leather is really great for daily gear. It's water proof and near indestructible. It's the kind of leather that if bent or scratched, the color gets lighter (called "pull up") but will return to original by gently rubbing it. Really cool and ages amazingly. Probably the last glasses case you'll ever have to buy. I use mine everyday and it just keeps looking better. It's a little stiff and inflexible but will loosen up after a while. If you're looking for a flexible and softer case, go see the standard case here:
For typical reading glasses.