If the ventilation holes are consistently small, these lids are the best around. But I did receive some with slightly larger holes than others. When the culture reaches the end of it's life, sometimes the last batch of flies are stunted enough to crawl right out the top through the holes. It wasn't fun to walk up to a counter covered in fruit flies to discover they were squeezing their way right through the holes.

No insects escape, these lids are great

The holes are consistent and doesn't let flies out.

For the same price go for the other lids. These can allow flies to escape and seem flimsier overall.