Make your mask even more effective with Heat N Bond sew-in interfacing. Working closely with The Masks Now Coalition, Therm O Web (the manufacturers of Heat N Bond brand products) has developed this new interfacing for use in the MasksNow.org 3-Layer Mask Pattern from Created for Crisis, as well as other patterns that call for lightweight 100% polyester nonwoven, sew-in interfacing. Try it today for an added layer of protection.