Deep form mortars with lips are glazed on the outside (except for the bottom) and unglazed inside. Oversized pestles are glazed to grinding surface. Resistant to thermal shock with an average coefficient of expansion from 20 degrees C to 200 degrees C is 3.56 x 10-5, gradually increasing to 4.69 x 10-5 at 1050 degrees C. Every batch of porcelain is heat tested in our factory. Every batch of porcelain is heat tested in our factory. No glaze-softening occurs up to 1000 degrees C and it is extremely white. Resistant to acids and alkalies, except for hydrofluoric acid. 275 ml capacity. 1 per pack.