Made of high quality, Borosilicate glass Cylindrical Dropping Funnel, made of high quality borosilicate glass Includes interchangeable plastic stopper, Socket size 23/32 1000ml capacity. PTFE Key Stopcock Perfect for any science or home laboratory 1000ml capacity. This cylindrical dropping funnel is made of high quality Borosilicate glass. Funnel includes a PTFE key stopcock and interchangeable plastic stopper. Socket Size 23/32. Funnel measures 16.5" in length. Eisco Labs Borosilicate glass has the following heat tolerances: Strain Point -515°C | Annealing Point 565°C | Softening Point 820°C.