Key Features Pack of 15 compatible biOrb airstones Aquarium airstones Suitable replacement for all biOrb filter systems Diffuses air into water supply reducing noise and large bubbles Essential to maintain oxygen saturation in biOrb Tank These pack of 15 compatible biOrb air stones are designed to fit with all biOrb aquarium filtration systems. It is essential to replace your air stones regularly, such as when showing signs of discolouration or a reduction in bubble rate. Replacing your air stones will ensure sufficient and clean oxygen for the aquatic life in your aquarium Specifications Compatible with all biOrb Aquariums Quantity: 15 Air Stones