All of our synthetic filter discs have a pore size of microns. We carry multiple sizes of filter discs: 29mm (for custommade spawn jar lids), 70mm (regular mouth jars), 90mm (widemouth jars), 110mm, and 125mm. In addition to our regular synthetic filters, we also carry a cellulose filter disc that is a recent innovation in the mycology field (70mm only). Please take your time to browse ...