Vacuum Tubes for the testing of the haemostasis system contain a buffered tri-sodium citrate solution with 3.2% citrate content (0.109 mol/L). Additive to blood ratio: 9:1. Tubes with 3.2% sodium citrate are used in the testing of the haemostasis system. The triangular filling mark helps to clearly determine an accurate additive to blood ratio, allows users to fill the tube properly and minimize the risk of diagnostic error.