Flask Volumetric class 'A', cap. 50ml, socket size 12/21, borosilicate glass, Blue Printing-EIS-CH0446D offers a thoughtfully designed, durable resource for hands-on learning. Made of high quality Borosilicate glass Includes chemical resistant polypropylene stopper, socket size 12 / 21 50ml capacity Class A. As per DIN ISO 1042 Standard Perfect for any science or home laboratory 50ml capacity. This Class A Volumetric flask is made of high quality 3.3 Borosilicate glass, and includes a chemical resistant polypropylene stopper. Socket Size 12/21. Tolerance ±0.060 ml. Autoclavable at 121°C. Flask stands 5.5". Base is 1.75" in diameter. Neck measures 4" in length and has a diameter of approximately 0.6". Eisco Labs Borosilicate glass has the following heat tolerances: Strain Point -515°C | Annealing Point 565°C | Softening Point 820°C.