Finding my old compass had a bubble I bought this to take on a navigation course, expecting to get a recommendation from the tutor for a long-term replacement. I expected it to be rough round the edges but in fact it was systematically inaccurate by 3-5 degrees, compared with both the map and the tutor's compass. I have selected a nice new compass and this one will stay in the drawer as a reserve (with a note to compensate for the error every time).