Description Description RCA / Burle JAN-1P21 Photo Multiplier Tube - Single Photon Detection Capable the classic 1P21 Photo Multiplier Tube! This tube appears to be new, although they do not wear out. 60 years after their inception, PMT's are still the most sensitive light detectors available! They can detect single photons! About 1/3 of all photons that reaches the tube are detected. Condition: Open boxThis tube appears to be new, although they do not wear out. View AllClose