These flat flange lids are used in conjunction with flat flange vessels as an alternative to the large volume round flasks. The wide neck opening of flat flange vessels allows easy access to the vessel contents. The two parts are held together by means of a clamping ring. The multi-neck ground necks on these lids allow the connection of a variety of other ground joint components such as dropping funnels, condensers and stirring shafts. Flat flange vessels are well suited for preparative work such as general reactions, distillations, evaporation and drying of solid and viscous substances. Their heavy wall construction and geometry make these vessels safe for working under positive pressure and vacuum.