Made of high quality, Borosilicate glass Cylindrical Dropping Funnel, made of high quality borosilicate glass Open top with PTFE Key Stopcock 50ml capacity Perfect for any science or home laboratory 50ml capacity. This open top, cylindrical dropping funnel is made of high quality Borosilicate glass. Funnel includes a PTFE key stopcock. Funnel measures 8" in length, and neck diameter of 1.1". Eisco Labs Borosilicate glass has the following heat tolerances: Strain Point -515°C | Annealing Point 565°C | Softening Point 820°C.