This Air Stone is a simple and great way to add oxygen to your protein skimmer and help it decrease protein in the water. Great for fish tank and aquarium use. It will be the good choice for you. Features -Color:Multi -Material:Wood -Size:6.50X2.30X2.20cm/2.55X0.90X0.86in - Useful: Fish tank bubbler Air Stone is useful and reliable, make fine bubble for increasing oxygen - Simple and Compact: Simple appearance and compact size, will not take up much fish tank space - Fine and Uniform Bubbles: Wooden air stone can produce very fine, uniform air bubbles, which can greatly dissolve and increase oxygen in water - Easy to Use: Easily produce fine bubbles that help to increase oxygen levels and circulate nutrition, useful and simple - Practical and Convenient: A good and practical Air Stone for your protein skimmer, practical and convenient Package list: 9 x Wood Air Stones