Upgrade your mask to have a filter pocket built in! Please select the quantity PER MASK you'd like to upgrade. If you are not upgrading your entire order, please leave a note at checkout indicating which mask is being upgraded. Thank you! **NOTE: THIS IS NOT A MASK LISTING. IT IS AN UPGRADE TO A MASK PURCHASE.** THIS LISTING DOES NOT INCLUDE A FILTER, ONLY ADDS A POCKET TO YOUR MASK TO INSERT ONE. Due to the nature of this product, I do not offer refunds/exchanges/returns on completed orders. Thank you for your understanding.