Nalgene 125-0020 Polystyrene with Cellulose Nitrate Lab Filter Unit, 0.2 Micron, 50mm Membrane Diameter, 150mL Capacity (Case of 12) Capacity: 150ml Cellulose Nitrate (CN) membrane diameter: 50mm; pore size: 0.2m CN filter is white and non-gridded Polystyrene housing unit has a GREEN collar Features a leakproof, 1-1/2 turn, threaded screw closure