Borosil® Amber Volumetric Flasks with Interchangeable Solid Glass/ Plastic Stoppers are manufactured from 3.3 Borosilicate I.D. control tubing. Each flask is individually calibrated with an automatic, computer controlled, calibration machine, providing a more accurate volume. Borosilâs Volumetric Flasks are designed to give the best combination of thermal shock resistance, physical strength and resistance to chemical attack. All Amber Volumetric Flasks have permanent ceramic white printing. Amber coating is on exterior surfaces to benefit use with light sensitive solutions. Comes with Batch Certificate. - 5mL to 20mL supplied with trapezoidal shape for better stability *Certified and Calibrated at 20°C