The 25x150mm 60ml culture tubes feature Type 1, Class B borosilicate glass construction, which prevents pH change in laboratory tests. It has well-rounded bottoms, fire-polished tops free of rough edges, uniform dimensions and convenient dispensing packages that keep them free from dust and other particulate contamination. It is resistant to chemical attack and weathering, avoiding leach out that contaminates solutions. Each tube is heat-treated at temperatures exceeding 500C (932F) immediately before packing, eliminating contamination, increasing strength, and reducing breakage. Tubes exceed USP Type I specifications.