Refurbished laser scanner assembly, for the HP Color LaserJet 5550, 5550N, 5550DN. (Not for use in the LaserJet 5500 series) HP part # RG5-7681 . You may need to replace a laser scanner if you are experiencing any of the following error codes on your LaserJet 5500: Error 51.10, 51.11, 51.12, 51.13, 51.20, 51.21, 51.22, 51.23 . There is one laser scanner for each of the 4 colors. NOTE: This is considered a major repair. Please check out our installation instructions to be sure you want to attempt the install.