Porcelain funnel features fixed perforated plate. Glazed on inner and outer surface except for the rim. 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. For filtered paper with 47 mm diameter and has approx 50ml capacity. 1 per pack.