The Julia 3-piece salt and pepper shaker set is made of green-rimmed stoneware. Stoneware is a clay-based material fired and baked at 1100-1300 degrees, commonly used for making plates and dishes. It is much more durable than ceramic and less porous, meaning it does not absorb water as much. Due to being fired at higher temperatures, it can be safely used in the microwave, oven, and dishwasher for many years.