Pretty tight. I will try to get a pic. Fixes with seatbelt as mentioned. What I do is after fixing with seatbelt, I pull seatbelt tight before closing aditional locking mechanism (orange belt lock on top left corner of seat pic). There is one of these locks on either side which is helpful.
Very rugged with alot of protection and the padding is easily removed for washing.
Downside is that it's a bit pricey and I dought (at least for my little guy) that it'll fit when he's in class 3...
Paulo