VACUETTE® Z Serum Sep Clot Activator Venous Blood Collection Tube Clot Activator / Separator Gel Additive 8 mL Pull Cap Polyethylene Terephthalate (PET) Tube (409479_CS) 1200/CSGreiner's Vacuette CAT serum separator clot activator tubes contain a separating gel that migrates up to the interface between serum and clot during centrifugation, where it forms a stable barrier and separates the serum from the fibrin and cells. 8 mL serum tubes come with an additive that serves as a clot activator and separator gel. Pull cap is color coded red with a yellow ring. Dimensions: 16 x 100 mm Clear, silica coated tube is made of