The model ‘G’ ( Geodetic) and the model ‘D’ (MicroGAL).

The model G has a repeatability of 0.01 milligal and accuracy better than 0.04 milligal. It has a world wide range of 7000 milligal and needs no resetting.

The model D has a repeatability fo 0.005 milligal and accuracy better than 0.01 milligal. It has a 200 milligal range. Resetting allows world wide use.

Both models have a negligible drift and a very stable calibration.