Serum-separating tubes, also known as serum separator tubes or SSTs, are test tubes used in clinical chemistry tests requiring blood serum.
SSTs are sometimes called "gold-topped tubes", "tiger-tops", or "marble-top tubes", referring to the stoppers which are either gold, red with a gold ring on top, or marbled red and grey. The stopper of SPS (sodium polyanethol sulfonate) tubes have a paler yellow color, sometimes causing confusion; these are known as "yellow tops" not "gold". Trademarked versions of the SST include Covidien "Corvac" tubes.