The PTT 3.2% Citrate non-vacuum tubes are manufactured by MB Lab Consumables. These PT/PTT tubes are designed in accordance to the 1:9 ratio of anticoagulant to that of the blood sample. These 1.8 ml 3.2% Citrate non-vacuum tubes are routinely used for coagulation studies. The additive added is Buffered Sodium Citrate. It is present in a 1:9 citrate to blood ratio. These citrate tubes with 3.2% buffered sodium citrate solution are used for routine coagulation studies. Sodium citrate has been use as an additive here because it is an effective anti-coagulant. It is used by blood banks and clinical laboratories. The ration of sodium citrate to blood is often 1:9. The mechanism of action here includes the citrate ions chelating the calcium ions present in the blood leading to formation of calcium citrate complexes. This leads to disruption of the entire blood clotting mechanism, allowing the blood to be carried and stored easily. Due to low toxicity of the buffer sodium citrate, blood can be stored for an extended period of time. These tubes have a blue coloured cap. The tubes are made from high grade PET material and are sterile as well as disposable. The tubes have the following dimension: 13 x 75 mm. They have a shelf life of two years.