This convenient system eliminates the need for syringes in many cases and reduces risky blood exposers to phlebotomist and need to transfer blood to test tubes by Lab technicians and consists of disposable needles and tubes. Evacuated tubes are made of glass or plastic and come in various sizes ranging from 2 to 10 ml. Evacuated tubes may or may not contain additives. Blood collected in tubes without additives will clot and yield serum on centrifugation. Tubes that contain additives may or may not clot, depending upon the type of additive they contain and makes testing more rapid and accurate compared to open blood collection and testing.