Twin Pack PLL Type UVC Germicidal Replacement Lamp PondH2o UV bulbs are designed for UV-C Filter Clarifier systems for both Ponds and Aquariums. Value Two Pack so keeps your filter effective for a full 12 months. Germicidal lamps operate at 253nm to greatly improve the efficiency of your filtration system when water passes by the UVC lamp. PondH2o UVC bulbs work to clear your pond or aquarium water by removing unsightly green algae . The strong ultraviolet light breaks down the algae in the water. For optimum UVC effectiveness, bulbs should be changed every 6-12 months. Please make sure that you are purchasing the correct 4 pin UV Bulb by checking your filters instructions for the desired bulb wattage and length ? Value Pack of Two 18 Watt UVC Replacement Lamp Bulbs ? 253 NM Range 8.6 Inches ? Industry Standard 220mm Length including Pins ? Average Effective Lifespan of 8000 Hours ? PLL 2g11 Base ? PondH2o is a Registered Trademark And Assured Quality We sell Many UVC Bulbs online, Check out our Store!! Terms and Conditions. We use all approved methods for taking payment. Sales Tax will be added to all shipments based regulations. We always try to combine purchases, please contact us directly for a personal service. You will be notified on the day that your goods have been dispatched via e-mail with tracking which is used on all purchases. Please note that if there are any problems, contact us first via e-mail giving full details of any problem along with your user ID. We use USPS and UPS as our chosen carriers shipments to Hawaii, Alaska Puerto Rico may incur surcharges, contact will be made to advise before shipment at which point the order can be canceled if desired. Orders placed on Saturday/Sunday Public Holidays will be processed next working day. We pride ourselves on excellent feedback, if any part of the buying experience is not to your satisfaction, please contact us to rectify before leaving feedback. By committing to buy you are agreeing to the Terms Conditions stated above.