This product, with UV sterilization function, can ensure the fish tank clear and bright effectively. It's very simple for use and great for effects. Features: High quality filament for high performance and energy-saving. Adopt quartz glass tube for high transmission of ultraviolet ray. Powerful suction cups for adjusting position freely. Safe water-proof design for totally submersible use. Suitable for controlling malignant bacteria in aquarium and fish tank. Specifications: Body Material: Quartz Glass Plug: EU Plug Voltage: AC 220-240V Frequency: 50/60HZ Wattage: 5W / 7W / 9W / 11W / 13W(Optional) Power Cable Length: Approx. 200cm / 78.7in Tube Diameter: 19mm / 0.75in Lamp body Length: 5W: 195mm / 7.67in 7W: 200mm / 7.87in 9W: 225mm / 8.86in 11W: 245mm / 9.64in 13W: 245mm / 9.64in Package Size: 28.8 * 8 * 4.5cm / 11.34 * 3.15 * 1.77in Package Weight: 5W: 258g; 7W: 259g; 9W: 245g; 11W: 271g; 13W: 271g Notice: 1. The sterilizer should be placed in filter-tank, can't put it in the fish tank directly. 2. The product is for submersible use. 3. In use process, please cut off the power supply and stop using immediately if the lamp enters water. 4. The ultraviolet radiation will cause direct harm to human skin and eyes, please don't expose to use. Usage Suggestion: Please choose the suitable lamp according to the size of your fish tank and filter-tank. 3-4 times for a week and 10 minutes-1 hour each time. If there has large number of algae in the aquarium or sick fish in the tank, can use this sterilizer 1-2 hours per day, but don't exceed 2 hours. When the symptom turns better, please return to normal use. Package List: 1 * UV Light Sterilizer