Back in 2018, I posted about the advantages of using media bags. The photo in that post included various sizes of bags that I use. Several months ago, I stumbled across some smaller mesh bags, 3″ x 4″ on Amazon, which I decided to try for some very specific applications.
These have turned out to work really well. They have a drawstring closure with longer than necessary string, which allows them to be secured either by simply tying them or just wrapping them around the bag.
If you have some smaller tanks or just want to use a little bit of chemical media, these bags are a great size.