I put one on with a magnet in a ball floating in fluid, but then noticed it slowing down and getting completely stuck as temperatures dropped. It went off as I ride year round and do not want misleading readings. Interestingly, a Swiss inclinometer I have on, with an air bubble in fluid, works fine year round. Given bad experience with the compass I wrote to the manufacturer of the inclinometer ahead of the purchase and they assured me that it would be fine and it turned out to be true. Next compass I got, with a potential to go on the bike, went into the freezer first and got stuck too. The issue might be with the type of oil that needs to be put into the compass.