Don't yet know how well it works... But I imagine, well enough.
I have justt put this into use. No results yet yet but it appears it will do the job quite well. Much nicer than my homemade version. The bottom part has a reservoir to put the attractant in (white wine works in this type of trap) I will then cut a few square inches of yellow sticky trap paper and place in the tray on top of the attractant. Check the measurements, these are larger than expected, a few should protect a room full of plants from gnats and other nasties.
only tested now for lack of flies: very good