Nalgene™ transparent polycarbonate Erlenmeyer flasks with polypropylene screw closures. Use for preparation and storage of culture media and many culturing techniques. Far safer than glass flasks for use in shakers. Closures are linerless and noncontaminating. Flasks and closures are autoclavable, but polycarbonate shows some loss of mechanical strength after repeated autoclaving. Before autoclaving, set closure on top of the container without engaging the threads.