Absolutely 1

Anyone who is traveling with kids in the car, knows the alternatives. Either food is strictly prohibited in the car, or it crumbles. These crumbs can then either accept with a shrug and so his car seats ruin (Schokokeks summer leaves a lasting impression), or you put something under. How did it first tried with cloths. It was cheap, but also annoying because they are always in place. Then we tried it with this document - and are completely satisfied. Does not slip, do not bother, even slightly reduce the footprints he leaves behind child seat after some time on the car seat. Then there are the storage options, of which you have never enough. And - we had not thought of, but it's true - even if you do not eat in the car, the small puddles hoppers are always a source of dirt for the car seat when they climb into their child seat. Again, the protective pad helps reliably.
It may sound picky, but I think once or twice a year Autoaussaugen should suffice. And even if you have small children, the car does not have to look so like a dump. If you want to implement this, you need small, handy helpers. In short - this is one.