Axygen microcentrifuge tubes feature a screw cap that provides a tight secure seal. Screw cap tubes are available in a variety of colors with a conical or self-standing bottom. Sterile options are also available.Maximum G-force is 20,000 RCF.RNase-/DNase-freeNonpyrogenicTubes, with Cap, SterileAll sterile screw cap microcentrifuge tubes are pre-assembled with non-looped caps with O-Rings.Colored-cap versions are also available in sterile format.