A Vacutainer blood collection tube is a sterile glass or plastic tube with a closure that is evacuated to create a vacuum inside the tube facilitating the draw of a predetermined volume of liquid. Most commonly used to collect blood samples in venipuncture, they are also used as urine collection tubes and as serum separator tubes. Vacutainer tubes may contain additives designed to stabilize and preserve the specimen prior to analytical testing. Tubes are available with or without a safety-engineered closure, with a variety of labeling options and closure colors as well as a range of draw volumes.