Pictures: Details: Compact Geiger Muller tube, the SBM-20M shows an excellent sensitivity for its small size. It was designed for hard beta and gamma radiation, and the particular tubes in my photos above are new generation tubes, manufactured in 2012. This is similar to the SBM-20-1, but smaller. Notes on sensitivity: The sensitivity of this tube is comparable with the SI-29BG and the SBT-9. Its small size makes it ideal…