Capsules contain layers of glass microfibers (GMF), ultrafine glass microfiber (UMF) and polyethersulfone (PES) membrane. This provides for serial filtration, which is especially useful in filtering serum or other hard-to-filter solutions. Useful in Virology, tissue culture and microbiology labs, in immunoassay methods and diagnostic standards and controls. Housings are manufactured from polypropylene, bonded and sealed with advanced fusion technology to reduce structure failures and leaching of the filtrate, without the use of mold releases, glues, powder metal, adhesives, epoxies or other extraneous material. Supplied with 3/8" to 1/2" step barb inlet and outlets. Manual vent control with luer lock can bleed air from upstream or serve as an injection port. Filters are sold individually.