The LABSOLUTE® hexagonal hollow glass stoppers with standard ground joint and pointed bottom are made of high-quality borosilicate glass 3.3 and are therefore extremely temperature-resistant up to 500 °C. The stoppers comply with the DIN 12252 form C standard. They are resistant to cold lyes/alkaline solutions and strong acids with the exception of hydrofluoric acid and concentrated, hot phosphoric acid. The stoppers can be easily combined with all glass products that have a ground joint like measuring flasks, Erlenmeyer flasks, round bottom flasks, etc.