VACUETTE® serum tubes are used in determinations for clinical chemistry and immunology, hormones, TDM and microbiological serology. Serum tubes from Greiner Bio-One are available in three versions: CAT Serum Clot Activator, CAT Serum Sep Clot Activator and CAT Serum Fast Separator. The inner wall of each serum tube is coated with microscopic silica particles (clot activator main component SiO2) which activate clotting when the tubes are carefully turned.