Tubes are marked in 1-mL graduations and have a capacity of 12mL. Tubes are helpful while transporting, centrifuging and decanting to guard against sample loss. Super tubes are made of break resistant K-Resin and Economy tubes are made of clear polystyrene. Tube caps fit both Super and Economy Tubes, providing secure closures during transport and storage. They also prevent the aerosoling of potentially infectious specimens during centrifugation. A flip cap covers one-third of cap circumference.