Check the listing for details. 32 Mushroom Filter Patch Self Adhesive 0.22 Micron 3/4inch - Spawn BRF Grain. Listed at 13.95 USD. These Self Adhesive 0.22 Micron Synthetic Filter Patches each measure 3/4" across. 1 sheet of 32 reusable filters specifically engineered for gas exchange These are a must if you're making substrate jarsCreates optimal air exchange for spawn, brf and liquid culture jarsReusable and autoclavableBeware of foam type gas exchange filter patches that are being sold as mycology gas exchange filters because they don't work at all This item ships in a 4"x8" padded mailer so watch for it in your mail as it is a small mailer. Drill a 7mm or 1/4" hole in the lid & remove shards of metal that may be attached to the hole after drilling. If the area where patch is to be placed is still not smooth lightly flatten it out by gently tapping it with a hammer while being careful not to bend the lid itself. Then place filter patch over hole on the top of the lid. We Do Not Ship To Unverified Addresses. Buyers Is Responsible For Providing Correct Shipping Address. We Are Not Responsible For Orders Returned To Us As Non Deliverable. Buyer Agrees To Pay Double The Actual Cost To Reship Order To Compensate Us For The Costs Of Returned Postage On Their Non Deliverable Order. As A Business We Pay To Have Non Deliverable Items Shipped Back To Us. No Refunds Given On Non Deliverable Orders.