These volumetric flasks are constructed of low-actinic amber glass, providing protection for materials that are sensitive to light. Each flask features machine-blown bodies and heavy-beaded, heavy-tubing necks that are tooled for standard taper glass stoppers. Each volumetric flask is supplied with a standard taper glass stopper which provides a leakproof seal. This airtight seal not only preserves the integrity of your samples but also enhances the reliability of your volumetric measurements. (6 per PK )