Borosilicate glass burettes offer accuracy, reliability and durability even after repeated usage. Each burette is individually calibrated for percision and high accuracy. All graduations are durable in white enamel. The burette stopcocks are specially ground so that they provide leak resistant operation. Burettes with general purpose (gp) screwthread stopcocks with PTFE keys offer excellent flow controll. Also, burettes with these gp stopcocks have unique Floun/glass seals that prevent leakage. Class B.