plastic shell and a foam liner that are both heat moulded in-store.
This means the shape of the X Pro 90 W can be personalised for your feet, resulting in more comfort for longer and therefore more time spent on snow, possibly the most crucial factor in improving your skills (as well as being more fun).
The better fit of a personalised fit also means better control, so helping you to develop your skills, whilst the 90 flex will allow you to push the boots reasonably hard too.
Add to that a choice of last widths of 100 or 106 and the X Pro will work for a wide range of foot shapes.