These origami fog stoppers can help reduce the fogging of your glasses in winter or during physical exercise. They do help, but they are not perfect. Model’s description mentions several non-origami alternatives.
In order to work, this model has to be folded from soft tissue paper (e.g. facial tissue). If the paper is not fluffy enough, fog stoppers will be too thin and will not be able to seal the mask properly.
The sheet does not have to be an exact square, but should be roughly so. You will need to fold two pieces, one for each side of your face.