These bags are 4 mil. Great for freshies, wax melts, crafts, jewelry, even snacks! They are the perfect size for nearly all cookie cutters. It even fits out 6 inch freshie! They are great for keeping the scent safer longer on your freshies, beads, and other scented products. Not to be used for "wet" oils. Use only on products where the oil has been dried. Keep out of the reach of children and pets.