Flask Boiling with joint 50ml, socket size 19/26, round bottom, interchangeable joint, single neck, borosilicate glass-EIS-CH0404B offers a thoughtfully designed, durable resource for hands-on learning. Made of high quality, heavy duty Borosilicate glass 50ml capacity Single joint with 19/26 size socket Stands 3.5" tall, neck measures 0.9" wide, and bottom diameter measure 2" Perfect for any science or home laboratory 50ml capacity boiling flask made of high quality, heavy duty borosilicate glass. Single, interchangable joint with 19/26 size socket. No stopper included. Flask measures 3.5" tall, and has a neck measuring 0.9" wide, and a bottom diameter measuring 2". Eisco Labs Borosilicate glass has the following heat tolerances: Strain Point -515°C | Annealing Point 565°C | Softening Point 820°C.