Fisherbrand Microcentrifuge Tubes 0.5mL Free standing Screw Cap Tubes with cap and % O Ring Sterilized Natural Fisher Sientific Screw Cap Microcentrifuge Tubes 0.5mL; Free Standing; with Screw Cap & O-Ring; Natural Optimized for secure short term sample storage in low temperatures. Offered in 0.5mL through 2.0mL volume capacity, these tubes are autoclavable, boil proof, and freezable to -80C. Find a selection of colored screw caps to improve sample identification in the lab. Amber tube options are ideal for protecting your light-sensitive samples. Screw Cap Microcentrifuge Tube Design Tubes are designed with conical bottoms allowing for more complete sample retrieval| 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 conveniencedash (em) the tethered screw cap is the solution when it is important to maintain the same cap with the same tube.