This is the replacement lamp for VIQUA VP950, VP950M and obsolete Sterilight SPV950, SP950-HO and SPV-20 Series UV systems. Installing a fresh lamp every 12 months is crucial to keep your system operating effectively. If you don't, the lamp's UV rays can gradually weaken until they no longer affect harmful micro-organisms. Sticking to a strict, one year change-out schedule is the best way to prevent this and ensure top system performance.