Nalgene 524 and 124 Series Filter units have naturally hydrophilic Polyethersulfone (PES) membrane and Low-Profile Polystyrene (PS) housing. An economical filter unit that's ideal for small-volume benchtop filtration and tissue culture work. Wide, stable base design. 564 series have Supor machV PES membrane which comes assembled with 50 ML conical tube and a separate closure. Includes 2 reusable stands in each case. Pore size and membrane type are printed in easy-to-see Blue color-coded collar unit. leak proof screw cap closure eliminates pH shift in receiver for longer life of stored media. Nonpyrogenic and noncytotoxic. Gamma radiation-sterilized and indicidually bagged for a 5-year sterile shelf life.