The R9110 is a 28 mm (1-1/8 inch) diameter, 9-stage, side-on type photomultiplier tube having an extended red multialkali photocathode same as the R3896. The R9110 features very low dark current, extremely high quantum efficiency, high gain, good S/N ratio and wide spectral response from UV to near infrared. The R9110 is directly pin compatible with the R3896.