Graduated Interval: 0.05ml Borosilicate glass burettes offer accuracy, reliability and durability even after repeated usage. Each burette is individually calibrated for precision and high accuracy. All graduations are durable in white enamel. The burette stopcocks are specially ground so they provide leak resistant operation. Burettes with general purpose (gp) screwthread stopcocks with PTFE keys offer excellent flow control. Also, burettes with these gp stopcocks have unique Fluon/glass seals that prevent leakage.