The lower part of a flat flange round-bottomed flask has a round-bottomed shape and its own for preprative work involving solid and viscous substances. Working under pressure or vacuum is possible.– Flange with groove: A sealing ring (O-ring) can be inserted into the groove, by means of which the vessel is firmly closed – Pressure and vacuum resistant due to the geometry and solid wall thickness – Use up to the technically maximum possible vacuum and thus maximum safety for the user (observe safety instructions) – Fired-on, highly durable white print – The lower part of a flat flange round-bottomed flask has a round-bottomed shape and its own for preprative work involving solid and viscous substances. Working under pressure or vacuum is possible.– Flange with groove: A sealing ring (O-ring) can be inserted into the groove, by means of which the vessel is firmly closed – Pressure and vacuum resistant due to the geometry and solid wall thickness – Use up to the technically maximum possible vacuum and thus maximum safety for the user (observe safety instructions) – Fired-on, highly durable white print –