This is an adjustable facemask spacer to keep the mask from coming in contact with your mouth. This particular design is intended for fabric masks that have a seam on each side of the mask. After sliding the two pieces together, clip the mask on each side of the mask and then adjust the slide to the proper size after test fitting to your face. Mark the excess at the sliding end and then cut with scissors. After getting the proper length, you can use a hair dryer or heat gun to place a moderate bend in the band if needed.