Our cultivation lids fit precisely on any "wide mouth" 90mm canning jar which are commonly used by today's cultivators. They feature a large high quality synthetic 22mm 0.2 Micron filter, the highest level of filtration available. Usage of these allows a fresh, constant air exchange while preventing the entrance of unwanted contaminates. Use them for cultivating and grain spawn or liquid culture media. The self-healing injection ports are made to withstand many inoculations and will not lose their shape like the plastic lids.