This is a cylindrical, heavy-wall reaction flask, except flat flange has an O-ring groove for use with CAPFE® (PTFE encapsulated silicone rubber) O-ring instead of a gasket

Without constriction at top to facilitate introduction/removal of material and allow for ease of cleaning. Flat bottom rounded into side wall. Flask is supplied with one CAPFE O-ring. Comes with 28/15 O‑ring ball joint for easy connect/disconnect from hoses, or #11 Ace-Thred. Made from borosilicate glass.