12 volt adapter socket is a different shape, it is angled, have already broken an angled one in my car because my 12 v socket is behind my gearstick and if the charger is pointing the wrong way when i select reverse i hear plastic breaking, but for the price will just have to be careful , prompt delivery though.
update 23/09/2013 whilst plugging charger into 24v socket of my l8t lorry the charger exploded and split in two. it was lucky i wasn't moving at the time and also lucky that my tomtom go510 wasn't on the cradle. so don't buy a charger unless it states it is compatable with both 12v and 24v
just ordered 2 more that stated they were 12/24v and received the same one's that have exploded in the lorry i was driving, not a happy bunny