Tubes are graduated and calibrated to contain. Centrifuge tubes are made of borosilicate glass Scale, legend, and marking spot are printed in durable white ceramic enamel, with the exception of tube 89002-190, on which the scale and legend are printed in permanent red stain. Heavy-duty tube is made with heavier walled tubing to withstand higher centrifugation speeds. The 10, 12 and 15 ml tubes are graduated in 0.1 ml increments. The 50 ml tube is graduated to 10 ml in 0.5 ml increments and from 10 to 50 ml in 1 ml increments.