added after market ones can be dangerous... we bough our land rover and it had on in it, it's a cheap one from china (found on ebay for less then $100 shipped) and mounted on the roof, well ours broke about 4 months after using it a dvd is stuck and won't play, eject, ect... anyways i was driving down a road i drive down atleast 4-6 times a day and i went through a smallish pot hole and it unlocked off the base and swung down and smacked me in the head, hard, if i'd have been doing faster then 20mph it could have prolly knocked me out and i'd have crashed... luckly also i had ds still in the rear jump seats in his parkway and his sister's radian in the middle seat and allie out board and the dvd swung back and hit her car seat, if she would have been in it she would have gotten hurt as well...
We will be buying a new one for our FL vacation and getting the ones that attach to the back of the head rests, we had them before and they worked out well.