I use it with a Garmin StreetPilot 7200, which is a fairly large, even somewhat clunky GPS with a large 7-inch screen.  The screen does vibrate just a bit when going down the road, but nothing major.  I have it sitting on the dash of an Armada, inside a slightly crevassed area just to the right of my steering wheel/main console.  It sits perfectly, so I can see it with my bi-focal sunglasses and still clearly see the road. I have had no problems with it sliding off or tipping.  It has a locking mechanism at the bottom, which I cannot slide over to lock the mount connection because the Garmin GPS is already wedged so tightly into the beanbag mount; no big deal though...doubt I would use it anyway, I don't see the need since it fits so securely without it. It is a well-made beanbag mount that I think will last a while and I got it for a great price here on Amazon.