The SBT-11 is one of the most popular and least expensive of the Russian Alpha radiation detector tubes. These tubes were categorized as “pancake” tubes in the trade, because their flat detection areas were shaped flat like a pancake, not cylindrical like most other detector tubes, allowing for fast surface scanning of people and things which might have been exposed to contamination by airborne radionuclides from nuclear accidents, testing, etc. Besides their Alpha sensitivity, the SBT-11 has a very high efficiency for detecting Beta radiation while still being very sensitive to Gamma radiation as well. This is an excellent choice for use in a handheld probe for the beginner or professional. *(The SBT-11 and the SBT-11A are identical except for a slight increase in overall sensitivity for the SBT-11A. They were both made at the same factory.) https://www.youtube.com/watch?v=CW2X5q3MKrk , https://www.youtube.com/watch?v=Pou4uCA_5s8 http://www.terranimpact.com/site/radiation/detector_