The ‘piece of plastic’ will help to stop the virus reaching the mucus membranes in the eyes, nose and mouth.
Hence face shields for medical staff & others etc.
Sorry to disappoint but only a fit tested FFP3 mask or PAPR (powered hood) will stop the virus. All other masks simply reduce the ability of the wearer to aerosol and infect others. It does not protect them. A piece of plastic is worthless.
Fit testing involves a third person who is trained to use fit testing equipment. That specification of mask is then approved for that purpose but many individuals fail with particular masks. Even if fit test is passed, a reusable mask has to be checked each time it is donned.
I happy to receive PMs but please dont just take a mask or piece of plastic and assume you are protected.
stay safe