Thermo Scientific Screw Cap Micro Tubes Screw Cap with O-ring Green Description Thermo Scientific Screw Cap Micro Tube caps with O-ring are designed to create a secure seal with the Thermo Scientific micro tube providing Pure Protection for sample preparation, transfer and storage applications. Tethered and non-tethered cap versions are available in a rainbow of colors. Screw Cap Microcentrifuge Tube Caps Design Screw caps with O-rings guard against leakage by forming a positive seal against the rim of the tube Tethered screw caps remain attached to the sample tube but can rotate completely for convenience--the tethered screw cap is the solution when it is important to maintain the same cap with the same tube O-ring is manufactured from durable ethylene polypropylene dimonomere compound Highest Quality Certified free of RNase, DNase, DNA and pyrogens Color/Packaging Options Standard Screw Cap Color options are: Blue, Green, Orange, Red, Yellow and Mixed to aid with visual identification of samples Tethered screw cap with O-ring: Natural