This glass outflow tube is suitable for most type of canister filter. This outflow tube bringing clean water from the filter back to aquarium. Moderate water circulation evenly is essential to maintain the water quality and prevent algae appearance. However, excessively strong out flowing of the power filter works negatively, hindering healthy growth of aquatic plants. Horn shape tube outflow is hydro-dynamically designed to create a moderate circulation of water which ideal for the growth of aquatic plants. Features: EXCELLENT APPEARANCE: Glass transparency give superb appearance to your aquarium. 2 SIZE OPTIONAL: Glass tube outer diameter 13mm(suitable for 12mm tube inner diameter of canister filter) and 17mm(suitable for 16mm tube inner diameter of canister filter). MODERATE WATER FLOWING: Deliver clean water from the filter with appropriate water flowing speed. Create a moderate circulation of water which ideal for the growth of aquatic plants. HIGH BOROSILICATE GLASS MATERIAL: Be