MetaPurex nano-porous aluminum oxide (AAO) ceramic 25 mm diameter discs with 60 nm pore size diameter.  Fits standard Lauer lock filter holder. Pore: local hexagonal packing (honeycomb) order with 60 nm  pore size of maximum variation 10%. Membrane thickness is 50 microns.  Micro-crack free heat sealed edges requires no o-ring protection, leaving larger filtration surface.