i use silva wrist models for a long time. never had bubbels troubel befor in those, but it did happened in a button silva after flight.<br>generally, the only model i know that is 100% relaibel is the heavy - duty army compass: it's a massive, most acuret 350 grams - much to heavy for a bagpack.<br>i suppose a good wrist silva, with a magnifed glass and measuring side marks, is the best. it wont give u the most acuret azimut - u'll miss a degree or two, but anyway, u alwayes follow tophografy & map and mostly using it to maintain direction. bubbels should'nt effect this featuar.<br>button campuses diverse: some filled with oil, or any other light solutions. filling flude qulity effects bubbels (and price).<br>anyway, if you break your main navagation compass and get to backup, all u can use it for is general direction only - u hardely can keep azimuth or re-azimuth with a butten.<br>a silva finger compass can do a better job: and, u can alwayes use your watch or the sun to verefay and get general estimation. (getting down a mounten during dark is a good recipy for troubels, and might be fatal: only night move is in desert conditions - and deserts r low, so, no bubbels....)