I have the Garmin 60csx. It's perfect for on and off-road purposes. It's water and dust resistent. It's compact so it's easy to carry, yet with a good sized color screen. It has a compass, altimeter, trip computer, excellent antenna etc. and the removeable memory card feature to easily change maps. I didn't want a bigger unit being bounced around in the 40 while I'm crawling over rocks.