Pondmaster UV Replacement Bulbs is the replacement UV Bulb for the Pondmaster UV Clarifiers. Average "Useful Life" is 9000 hour - A good rle of thumb is to replace every year at the beginning of pond season for best results! Pondmaster UV Bulb Specifications:- 10 Watt UV Bulb - Fits Pondmaster 10 Watt UV Clarifier- 20 Watt UV Bulb - Fits Pondmaster 20 Watt UV Clarifier- 40 Watt UV Bulb - Fits Pondmaster 40 Watt UV Clarifier 10, 20, 40 watt UV bulb - Quantity 1 per package. Clean or Replace Quartz Sleeve when replacing UV Lamp. Pondmaster UV Bulb has a 4 pin base. Pondmaster UV Clarifier Replacement UV Bulb - Aquarium UV Sterilizer Bulbs