Premium Class A Borosilicate Burette Capacity = 50mL with 0.1mL Graduations and 0.05mL Tolerance Glass Key stopcock requires lubrication but offers the smoothest, most authentic control. Designed to store liquids in the laboratory, but can be used in the home as well -- or even for beer and wine making. Please clean thoroughly before first use. Premium borosilicate 3.3 glass burettes Eisco Labs Borosilicate glass has the following heat tolerances: Strain Point -515°C | Annealing Point 565°C | Softening Point 820°C. Calibrated for delivery. Eisco Labs proudly manufactures its own products using state-of-the-art equipment, and following the highest standards of quality control. Each product is carefully designed by a team of laboratory professionals and experienced engineers with quality and durability in mind. They are manufactured with only the highest grade, raw materials and according to international quality standards to ensure that they can withstand use in even the toughest laboratory environments.