This is an Amperex/Philips/Photonis XP2202/B 10-stage 51 mm (2 in) photomultiplier tube. For over forty years, Photonis has been the leading manufacturer of fast PMTs for the physics research community. From 1956, with the introduction of the world’s first fast PMT until today, Photonis has constantly set the standard in timing and linearity. Tubes such as the XP2202 are still the preferred choice in the most demanding time-of-flight (TOF) experiments, some twenty-five years after their introduction. The excellent gain stability and high sensitivity of Photonis’ tubes, resulting from two decades of gamma camera tube experience, has made Photonis' PMTs the preferred choice in many large physics calorimeters.