This Rapid-Flow™ series polystyrene filter unit has a 250mL upper with a 250mL receiver. This product is not intended for use in direct patient care or diagnostic procedures. Red collar. Material: Polystyrene with a nylon membrane. Membrane diameter: 50mm. Pore size: 0.2µm. Upper capacity: 250mL. Receiver capacity: 250mL. 12/Case. Nalgene® #: 153-0020.