These borosilicate glass cylindrical reaction vessels have a tooled flat flange with an O-ring groove for a greaseless seal. Suitable for vacuum operation. Wall thickness is uniform throughout flask. Note: Use LG-7316 clamps. Scientists rely on the expertise and artistic skills of Wilmad-LabGlass' engineers and glass specialists to manufacture NMR and EPR consumables and laboratory glassware of the highest quality. Used daily in academia, healthcare and chemical, petroleum and other industrial applications, Wilmad offers 7000+ items as part of their standard catalog as well as custom fabrication for individual glassware, glass repair services and OEM glass parts.