Borosil® Solid Penny Head Glass Stoppers are the best in class for glass stoppers. Manufactured with low extractable quality grade USP Type I, 3.3 Borosilicate Glass and conforming to ASTM E438 Class A requirements means a reliable, durable, and useful glass stopper for your volumetric flasks or other storage media. In collaboration with Borosil Glass Works, Foxx Life Sciences is proud to bring the outstanding quality of Borosil® Type 3.3 Borosilicate glassware to North America for the first time. Manufactured from the same USP Type I, Borosilicate glass that North American scientists have come to trust, Borosil® Laboratory Glassware offers unparalleled mechanical strength, clarity, and reliability at competitive prices. And thanks to a unique annealing process, Borosil® Glassware is stress-free and incredibly resistant to thermal shock. We encourage you to send any questions to email@example.com or call 1-603-890-3699.