Pyur Scientific Glass Reagent Bottles are constructed of high-quality, low-expansion borosilicate glass in conformance with ASTM E-438 TYPE 1 CLASS A glass and DIN ISO 3585 Standard Borosilicate Glass 3.3. Each bottle features easy-to-read scale measurements and a large labeling field for easy marking, all in a durable white enamel finish. Pyur Scientific Glass Reagent Bottles also feature a silicon-sealed bottle cap. Each reagent bottle is expertly crafted with precise, uniform wall thickness, meeting the standards of lab-grade equipment.