When they were first produced there were some reports of leaking microwaves and warnings for pregnant women. But that went away long ago. I suppose one with the highest power rating would have the most shielding. A nice big one from goodwill for about 5 bucks is what I would get. I have a little one my daughter was using in her apartment and gave it up. I kinda want to line the walls of my wife’s walk in closet with aluminum foil just to see what she does.