These heavy duty PYREX® conical centrifuge tubes have durable white enamel graduations and are made to the same O.D. and length specifications as C1880, but with increased wall thickness for greater mechanical strength. In order to conform to outside diameter and overall length limitations imposed by centrifuge rotors and supports, it has been necessary to reduce the capacity these heavy duty tubes. The 12mL size is graduated upward from tip in 0.1mL divisions. The 40mL size is graduated upward from tip in 0.5mL divisions to 10mL and from 10 to 40mL in 1mL divisions.