This UV lamp is a genuine Viqua replacement lamp for VIQUA D, D4, VH410M, D4 Premium, D4-V, C4, C4-V, Viqua IHS22-D4, and IHS12-D4 Model UV water treatment systems. The Trojan UV lamp is a key component of your UV system as the light inactivates microbes, such as cryptosporidium, giardia, E. coli, legionella, norovirus, and hepatitis A virus †, as they pass through the UV rays. Replacing your UV bulb on schedule ensures you get the best water your system can offer.