The G-881b, as the name suggests, is a variation on the G-881 mini marine magnetometer and it has the same superlative specifications as that product.
Clickable thumbnail images of the G-881b are included so you can see the mag, the first of which has already been shipped to a contractor in Europe. The G-881b operates from the same high strength 61 metre long cable as does the marine system, but has the "T" housing on the tube removed, to allow the sensor to be held vertically and allows use in boreholes. Depth rating and other performance features are as per the G-881 data sheet.
Over the past few years Geometrics have had many requests for
shallow borehole magnetometers for deep UXO location, where bombs
may have buried themsleves in soft sediments to a depth
that precludes detection from the surface. However, in site
investigations on such sites, many boreholes are drilled for
foundation stability studies, soil and rock strengh analysis.