Super sensitive Geiger counter uses the popular SBM20 Geiger mueller tube and is sensitive to Beta and Gamma rays. Produces clicks and flashes of red when cosmic rays strike the super sensitive tube. Operates from one 9V battery (not included). Size about 1.3" X 4.6". Has aqua blue "on" LED. Uses only about 14mA for operation.
Here in Arizona the background click rate is about 20 to 30. This counter comes with the G21144 radium watch hand check source! Brand new-fully assembled-no case available.