Abstract: A facemask is provided that is made from a clear thermoplastic polymer with a sufficiently low glass transition temperature that a customer may engage in post-sale customization of the facemask. The facemask is configured to be heated and then reshaped by the customer, so as to better fit the customer's face. The facemask may include filter cavities or filter adaptors that conveniently hold removable filters. Methods of manufacturing a set of a plurality of facemasks, matching a customer to an appropriately sized facemask, and then enabling the customer to engage in post-sale customization are also provided.