KB Farm Self Adhesive Breathable Filter Discs (sheet of 20)

These self adhesive, sturdy, breathable filter discs are designed to keep bacteria and pests out of your enclosures while allowing easy transfer of air.  The discs are approximately 4 cm in diameter and are effective for holes up to 22 mm. 

Larva containers and breeding boxes are the best situations for using the filter stickers. Be sure to make the air holes on the container small enough so that the beetles/larvae can not chew through the filter disc and escape. I've found that these discs allow a better transmission of air than micropore tape, although both have their proper uses.  KB Farm is a well known manufacturer of quality Japanese beetle supplies so buy with confidence.  

The filter disc stickers are sold in sheets of 20 stickers and are priced per sheet.