These 10mL Pyrex® conical centrifuge tubes are used in connection with the Wasserman test. Also used to measure H2O content and potassium ions in oil muds. API RP 13B standard testing method. They are graduated in 0.1mL divisions up to 4mL, and 0.2mL divisions from 4 to 10mL. Tolerances: to 0.5mL ±0.02mL; 0.5 to 2mL ±0.04mL; over 2mL ±0.1mL. Graduations are durable white enamel.