Flask Distilling round bottom, cap. 250ml, borosilicate glass, three neck at angle, centre socket 24/29, side socket 19/26-EIS-CH0418O offers a thoughtfully designed, durable resource for hands-on learning. Made of high quality, heavy duty Borosilicate glass 250ml capacity Three necks at angle, with interchangeable joints. Center socket size is 24/29, side socket sizes are 19/26 Stands 5" tall, and measures 5.5" wide. Base diameter is 3.25" Perfect for any science or home laboratory 250ml capacity boiling flask made of high quality, heavy duty borosilicate glass. Three necks at angle, with interchangeable joints. Center socket size is 24/29, side socket sizes are 19/26. No stoppers included. Flask measures 5" tall, 5.5" wide and has a bottom diameter of 3.25". Eisco Labs Borosilicate glass has the following heat tolerances: Strain Point -515°C | Annealing Point 565°C | Softening Point 820°C.