Manual Modified Westergren system used for determining the erythrocyte sedimentation rate (ESR) of whole blood in 30 minutes using 1.2 mL Streck ESR-Vacuum Tubes Rack will accommodate up to 10 tubes simultaneously Rack exhibits >96% correlation to the standard 60-minute manual Modified Westergren method ESR-Vacuum Tubes are prefilled with 3.2% Sodium Citrate anticoagulant to ensure correct dilution when blood is added up to the indicated fill line Adjustable feet and leveling bubble on rack ensure that the tube is maintained at 90 degrees to the horizontal during testing for optimal performance Broken clips can be remedied using replacement clips for the rack