250ml Capacity Screw Type Rotaflow Stopcock Made of 3.3 borosilicate glass Socket Size 19/26 Plastic stopper included 250ml Separating Funnel - Borosilicate Glass, Pear Shaped, with Stopper and Rotaflow Stopcock Eisco Labs Borosilicate glass has the following heat tolerances: Strain Point -515°C | Annealing Point 565°C | Softening Point 820°C.