Purely UV-C Replacement Bulbs T5F BasePurely UV-C Replacement bulbs offer a much higher concentration of ultraviolet light than even the sun, making them highly effective as a cleaning and purifying agent for pond and aquarium pumps and clarifiers.What is UV and How Does it Work?UV light is germicidal - i.e., it deactivates the DNA of bacteria, viruses and other pathogens and thus destroys their ability to multiply and cause disease. Specifically, UV light causes damage to the nucleic acid of microorganisms by forming covalent bonds between certain adjacent bases in the DNA. The formation of such bonds prevent the DNA from being unzipped for replication, and the organism is unable to reproduce. In fact, when the organism tries to replicate, it dies.What are the Beneficial uses of UV Light?Ultraviolet technology is a non-chemical approach to disinfection. In this method of disinfection, nothing is added which makes this process simple, inexpensive and requires very low maintenance.How do Ultraviolet Water Purifiers Work?UV water purification units contain one or more germicidal ultraviolet lamps. The germicidal lamp is a short wave low pressure mercury vapor tube that produces ultraviolet wavelengths that are lethal to micro-organisms. This wavelength is in the region of maximum germicidal effectiveness and is highly lethal to virus, bacteria and mold spores. Therefore, the water or air that passes through the chamber is exposed to the germicidal UV light and the genetic material of the micro-organism is deactivated, which prevents them from reproducing and renders them harmless.Reference Tool for choosing the correct UV-C Replacement Bulb:Match your existing bulb to one of the bases.Match the wattage or length of your bulb. Some bulbs have a different length for the same wattage -- so be sure to match both watts and length.H-Series:The Purely UV L-Series carries the industry standard 2G11, G23 and GX23 base.The "H" is for the H-look with parallel glass connected by a glass cross piece at the bulb end.G23 Group:Works with units having magnetic ballastsG23 base has 1 molded snapGX23 base has 2 molded snaps2G11 Group:Works with units having magnetic ballasts2G11 base has 4 brass connecting pinsL-Series:The Purely UV L-Series carries the industry standard T5B, T5F and T8B base.The "L" designation indicates a linear bulb.Bulbs in the L-Series are either in the LB Group or the LF Group.LB Group:"LB" designates linear bulb with bi-pins, or connecting points at both ends of the bulb.T5B Mini has 2 brass connecting Bi-pins at each end of the bulb. Bulb is 15mm wide.T5B Medium has 2 brass connecting Bi-pins at each end of the bulb. Bulb is 25mm wideLF Group:"LF" designates linear bulb with four pins, or connecting points at one end of the bulb.T5 4-Pin Base is 15mm widePurely UV-C Replacement Bulbs are 100% quartz lamps that are warranted for 9000 hours of continual use and should be changed every 6-12 months to insure their effectiveness.