Application: It consists of an inner tube made of PP and an outer tube made of PET. Inner tubes made of PP can avoid additive decrease, which maintains the concentration of sodium citrate stable. Outer tubes made of PET can guarantee vacuum stability for a long time. It is filled with buffered tri-sodium citrate solution and citrate concentrations of either 0.109mol/L (3.2%) or 0.129mol/L (3.8%). It is mainly used for the test or blood coagulation mechanism and it can provide an excellent condition for the test of PT, APTT values.