Globe Scientific Tube Closure Polypropylene Screw Cap Natural For Sample Tubes with External Threads NonSterile (711477_PK) 1000/PKThese tubes and caps have been designed for the storage and transportation of biological material The screw caps are manufactured from non toxic polypropylene and offer strength and clarity This along with a polypropylene inner lip ensures a leakproof seal, even at changing temperatures The caps feature a long skirt and a super fast thread design that allows them to be removed or sealed with a single turn Autoclavable