IMPROVACUTER® ESR Tube (4NC 0.109M)/( 4NC 0.129M) contain a 3.2 % buffered tri-sodium citrate solution (0.109 mol/l). The mixing ratio is 1 part citrate to 4 parts blood. IMPROVACUTER® ESR Tube (4NC 0.109M)/( 4NC 0.129M) are used for the collection and transport of venous blood sedimentation rate testing. ESR measurements refer to the Westergren method.