I don't do many reviews, but I purchased this compass and after actually using it in the field have a couple comments on it.  I brought this compass on a rigorous 2 day land navigation course.  Like many others have stated, the compass housing shifts around, maybe by 1 or 2mm.  This can cause an error of a degree or so in your readings.  While obnoxious, the margin of error is very slim and in my experience was not the cause of any real life navigation mistakes.  If you always "set" it to the same side, your offset will be consistent and should not interfere with your measurements.