Coconut Activated Charcoal Carbon Filter for Grow Rooms: Multiple Sizes Available (4" x 10") Superior small hole construction and high-performance absorption. Large specific surface area and high adsorption capacity. Adsorb particulate faster and more effectively than other carbon. 950 high iodine adsorption value, much stronger adsorbing ability. 53% open hole area by professional design to allow more air flow to get through.