The Model 133 Series of Geiger-Mueller (GM) gamma survey detectors can be used with any portable ratemeter, scaler instrument, or area monitor that provides the appropriate amount of voltage (see specifications) with an input sensitivity of 30 ± 10 mV.

Waterproof versions of these detectors (all 133-x-1 versions) have the same characteristics as non-waterproof models, other than they are waterproof, contain an O-ring, and do not have a “C” connector on the probe end (base). A 30-meter (100 foot) cable is hard-wired into the detector. They weigh slightly more and have a slightly larger diameter than the non-waterproof versions. They are submersible up to 30 m (100 ft).