PYREX™ Heavy Duty Conical Centrifuge Tubes With White Graduations And Screw Cap manufactured by Corning are made 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. Tubes are graduated to 10 mL in 0.5 mL divisions, and from 10 to 40 mL in 1 mL divisions. Graduations are in durable white enamel. Tubes have pourout spout for easy decanting.