Product review (5 stars): Works fine.
As you would guess, it's relatively easy to make a repeating-pattern plastic mesh, wrap it around itself thirty or so times to make a filter, and glue the result together. This is essentially a textbook example of a plastic mesh glued to itself.

Note, however, that cat claws are attracted to plastic mesh over considerable distances. Best to keep these on a high shelf, behind a locking door.