Round Bottom Flasks (Boiling Flasks), made from high quality heat resistant Borosilicate glass. Uniform thickness with a heavy beaded rim.Accurate to within 5% of rated capacity. Round Bottom FlaskRubber Stopper Sizes  25 ml # 250 ml # 4150 ml # 5250 ml # 6500 ml # 71000 ml # 83000 ml # 10