Rugged cylindrical reaction flask Duran, flat, ground flange and O-ring groove, with an Easy Action Plug bottom outlet with Chemraz O-Rings for draining contents. For use with 6517 quick release clamp. Each flask is supplied with one CAPFE O-Ring (PTFE encapsulated silicone O-Ring). Plain silicone O-Rings are also available. The 1000-6000mL sizes feature an Easy Action 28/15 ball joint bottom valve while the 10 liter and above sizes feature our flush-seal drain valve bottom outlet.