Kimble kimax volumetric flask with ptfe stopper flask with a graduation ring blasted on the neck calibrated to contain with a marking spot on 10 ml and larger sizes the 2 ml size is test tube-shaped. All other sizes are of a conventional flask shape supplied with a ptfe standard taper stopper which has a color-coded handle replacement stopper is 41901r the 5 ml and larger sizes are designed from astm specification e288, class a requirements manufactured from 33 expansion, low extractable borosilicate glass conforming to usp type i and astm e438, type i, class a requirements. Warning: this product can expose you to chemicals including tetrafluoroethylene, which are known to the state of california to cause cancer. Prop 65 warning