Beware the Etrex mount listed elsewhere does not fit the Etrex 10/20/30, so you need this one.
It fits nice & securely on the stem and my Etrex is locked tightly even mountain biking, so this is a great mount.
I didn't give this five stars as trying to get my Etrex off the mount was a nightmare! I looked at it carefully and when locked in, the top of the mount is touching the Etrex body and unclipping it, makes it touch more. I got around this by filing the ends of the runners to make them a little thinner, just at the end (top of Etrex) and now it is easy to remove, yet still just as secure.
I assume the reason for needing to do this is because this mount is not designed for the Etrex, but I guess it has the same battery cover.
Oh finally, when fitting this mount to your Etrex, whatever you do, make sure the battery cover screw is locked in the closed position, else you'll be swearing, believe me!!!