There are two types, one that you stick on the outside of the door and one type where they insert into the window track. Mine are the latter and have held up well so far. They don't scratch the window because the glass is harder than the plastic but even the bits that do contact each other are inside the track of the window and can't be seen.
http://www.ebay.com.au/itm/For-07-15...-/262336186753
If you do get ones like that, file the edges that will contact with the window so there is no risk of the window getting caught on the visor edge.