It has a sticky pad so it is firmly fixed in place, it does come off easily if pulled from the edge if needed, ours started off in the van then into the car and back into the van I ordered another this morning so they can stay in place.
I think that you can wash the sticky but with WUL under the tap to bring back it's full stickiness but not confirmed it yet.
I got another as it is an option for putting the phone and you can also run two sat nags, the car one is a bit pants anyway, it works but only on a very basic level, G maps via AA is much more bettered and you can use the mic, in fact stupidly it is the only way you can use the mic.