HUAOU 40mm glass funnel is made of 3.3 Borosilicate glass, which has perfect chemical resistance, heat resistant, acid and alkali resistant, good thermal stability, laboratory grade glassware. Its designed to pour liquid into the container which has a small inlet. When filtering, the filter paper should be loaded into the funnel. Choose different filter paper according to the different requirements of filtration, and purchase the corresponding size filter paper according to the size of the funnel. Recommended size of filter paper for 40mm funnel: 7cm.