The SBM-21 Geiger tube offers relatively good sensitivity especially when compared to its ultra compact size.
The STS-5 is a geiger tube for hard beta and gamma detection, manufactured in USSR in the 60’s, similar in specs to the newer SBM-20.
SI-3BG Geiger tube is suitable for detecting high radiation doses, but finds little use in DIY applications.
Pictures: Details: The SI-22G is a highly sensitive hard beta and gamma radiation detector tube, made in USSR during the 80’s for the Soviet Military Needs by the Soviet Institute for Scientific Radiation Technology Research. Notes on sensitivity: This is a highly sensitive tube, thanks to its cathode material and relatively large size. It is perfect for monitoring equipment and DIY dosimeters, superior to the SBM-20 in this sense. The…