Caps with O-rings, amber, polypropylene, amber cap, irradiated, 20,000 x g Free of RNase/DNase, human and mouse DNA, pyrogens and endotoxins, sterilizable models available O-ring design, thickness and material selection are optimized to provide protective properties to maximize sealing ability, biological interaction and temperature adaptability Colored caps are available, with multiple color options for separation, coding and tracking of samples, amber is suitable for UV protection Can withstand RCF of 20000xg.