Globe Scientific's plastic micro hematocrit capillary tubes are completely unbreakable. They eliminate the risk of injury and contamination associated with glass tubes due to breakage. Plastic micro hematocrit capillary tubes comply with FDA, NIOSH, CDC and OSHA safety recommendations.The tubes are available plain or with an anticoagulant (sodium or ammonium heparin) that keeps the blood from clotting. All of the tubes have color coded ends to easily identify the plain and heparin treated tubes.