I replaced the stock mirrors, on my WR250R, with Doubletake mirrors. Doubletake mirrors [www.doubletakemirror.com/] mount on RAM arms/balls and allow you to adjust the mirrors to a multitude of positions including folding them inboard when riding offroad. I've found folding them in unnecessary, so far, since the mirrors are very robust and there is just enough give that they move rather than break, on a tip-over.
When I received them, installation was simple. I used a 1" RAM ball in each mirror socket (using the stock thread-reverser on the right side). I used the 3" aluminum RAM arm. I'm used to using RAM mounts, so adjusting these just seems natural. Here are some pics sitting in the yard.
There have been some reports of the mirrors moving while riding in rough terrain or at highway speeds, but I've experienced mirror movement in only isolated instances. They generally stay put. One possible reason could be the type of RAM arm used (Aluminum vs. Plastic) or simple variations in manufacturing tolerances.
The few that have experienced mirror creep have said wrapping the ball will a couple layers of electric tape has solved the issue. A trick to keep in mind if one experiences unwanted movement.
[The following was written Nov. 10, 2010 which will make sense when the weather is referenced]
I have also been using one of these on my ATV all summer. I now have a total of three mirrors and three 3" RAM arms and then have a total of 5 the RAM ball mounts for mirrors (on both of our dual sport bikes plus one on the left front rack of my ATV). Also have ball mounts and arms for GPS (I'm a big fan of RAM mounts). I easily move the three mirrors around between all three.
For bikes and ATV, I recommend the 3" RAM arms over the 2" arms and make sure you get the aluminum arms and not the cheaper plastic ones. The 3" arms get the mirrors further out so you can see past your arms and shoulders better. If you don't want them to stick out so far, you can position the arm to go straighter up and then just the mirror angle out. With the 2", if they are not long enough, you are out of luck. It's just a matter of having more adjustability/options with the 3".
It's negative 1 degree F. here right now and snowing and blowing, but I guess I can head out to the detached garage to snap a picture of the ATV setup. If you don't hear from me in 15 minutes, send the search and rescue dogs...
OK, I survived. I didn't back the ATV out (see prior comment on current weather), but here are a couple shots so you can see the Doubletake Mirror mounted on the front rack. This works great and, on the ATV, I like it better than the bar mounted mirror. Plus, with the winch controls, etc. bar real estate was at a premium. I was surprised to find out I preferred the mirror on the front rack. It's give a great perspective, though not as wide of a view as if one were looking at the reflection from a closer position.