Just a few added comments about the 530. i do not keep them on all the time so they did last me for the whole week in upstate new york last week. I was also using them for geocaching and they got me within 3 yards of what i was looking for each time. and the last thing i would like to say is that i left a unit with my brother while i was hiking, there was a large mountain between us, distance about four miles, and he was able to not only talk to me, but keep track of me as i was hiking along. oh, i downloaded maps of upstate new york into the unit, covered everything from just below syracuse all the way up to canada and still had room for more. i really like these units.