SIBATA 2306A-Series Volumetric Flasks meet ASTM E-288 Class A Specifications & USP Standards for Volumetric Glassware. These flasks feature machine-blown bodies and heavy-beaded, heavy-tubing necks, tooled for ST stoppers. The graduation line is sharp and permanent; large, white, block-letters allow the labeling to be easily read. Features a large marking square. All sizes are supplied with glass ST stopper.