This is a money saving option for Covid-19 mask protection. It is recommended that a washable mask be purchased that allows for the insert of this filter fabric.  Non-woven fabric, compared to woven fabric, traps much smaller particles like the Covid-19 viral particles.  It's also suggested that the bridge gaps around your nose be blocked with the use of a nose strip.  Aluminum nose strips with an adhesive can be searched for and purchased to be used on your mask to do this.