Floating core magnetometers are primarily for measuring the horizontal component of the earth's magnetic field.  Because the earth's field has a vertical component which varies around the world, the floating core fluxgate devices always resolves only that part of the field which influences a core which is held in the horizontal plane. Autonnic's range includes both damped and undamped types as well as 3 sizes: for tilt angles of  +/- 20, 35 and 45 degrees.