VACUETTE Venous Blood Collection Tube Pull Cap Sterile 454334 50 Count Greiner Vacuette coagulation tubes with sodium citrate are used for determinations in coagulation tests. The additive trisodium citrate contained in the tube prevents blood coagulation by binding Ca-ions. Vacuette coagulation tubes are also known as sandwich tubes due to their double-wall-technology. The inner tube is made of PP (polypropylene) and prevents the evaporation of liquid. The outer tube is made of PET (polyethylene terephthalate) and guarantees a correct draw volume. 13 X 75 mm Coagulation Tube