Hi, I read on an old post that an electrical converter requires a plastic connector to fit the 2cm recess in the Czech outlets but it wasn't clear if this plastic connector is necessary when using a adaptor. It seemed like the connector was only needed for a converter and not an adaptor. Thanks v. much.
I've never seen one with a recess.. you get the two holes for the prongs on your plug, plus one prong on top that goes into the hole in your plug. I don't think you need anything extra on top of the adapter.