All three layers of our mask are made from the same knitted 100% organic, 220gsm, GOTS certified, cotton fabric. This special blend of fabric makes our mask very breathable and comfortable to wear. We do not use woven fabrics as we found in our research and development that it significantly increases difficulty breathing. When wearing a mask with woven fabrics for an extended period (over 1 hour) or during modest physical activities, it eventually becomes difficult to breathe. This can cause wearers to remove the mask multiple times during the day. To compensate for this, we found that adding a third layer of our knitted fabric was able to boost protection, while making it significantly easier to breathe. Our masks also include a pouch for inserting an optional filter which allows wearers to increase the level of protection at their discretion. This effectively creates 4 layers for the wearer. The stiffener also plays an important role in creating a better seal around the nose to prevent particles from being inhaled around the mask.