Microcentrifuge Tubes 2.0mL Graduated Free Standing Screw Cap Tube with Cap & O-Ring/sterilized Natural Fisher Scientific Thermo Scientificâ?¢ Screw Cap Micro Tubes robust design and material selection are well suited for work with biologics and offer rich features, including ultra-clear externally threaded tubes and UV protective amber tubes. Options are available with or without a self-standing skirted bottom, non-knurl, and knurled tubes for single-hand operation, in 0.5mL, 1.5mL, and 2.0mL sizes, and the option of multicolored caps, with or without tethered straps. Screw Cap Micro Tube Caps offer a durable design incorporating an O-ring that helps prevent leaks under demanding conditions.