All of these filters come with an asymmetric polyethersulfone (PES) membranes. The asymmetric PES membrane is an extremely clean, low-extractable, fast-flowing membrane. It provides excellent throughput and low protein binding of media and other solutions. The 0.2µm pore size membrane provides a last line of defense against bacterial contamination.Complete units come with a bottle-top filter and a receiver storage bottle. Bottle-top filters have side arms fitted with quick-disconnect tubing adapters and screw securely into 33mm or 45mm neck size bottles.