20 mm adhesive synthetic filter disk sticker for mushroom jar lids. These adhesive sticker filters allow for gas exchange while providing filtration down to 0.23 microns. Autoclavable. These filters are disposable (one-time-use) and can be easily adhered to the top of a mushroom spawn jar lid to provide for gas exchange. Filters can withstand sterilization temperatures and are easily removable without leaving residue. These filters will cover any hole up to 3/8" inch in diameter and should be drilled with a 3/8" Forstner drill bit.