Coated with micronized silica particles which activate clotting when tubes are gently inverted Tubes with gel contain a barrier gel on the tube bottom that during centrifugation moves upward to the serum-clot interface to form a stable barrier, separating serum from cells Molded to be virtually unbreakable, providing a better level of safety than glass Tubes have an 18-month shelf life from the date of manufacture Pediatric tubes come with white rings for quick identification Safety Twist Caps can be removed and replaced several times Nonscrew caps can be removed and replaced as often as required