Model: ST-135 Made of ceramic material, with breathable and have an effect on purifying water in fish tank. Great shelter for shrimps, small fishes, baby fishes and other small aquatic animals. Offer the natural environment feeling and It is vividly and color detailed to add lively life to your tank.Tips: 1.Clean the product in cold water for removing dirt before putting it into your aquarium. 2.Allow about 1cm difference due to manual measurement.