with most liners, if you pull them out of the shell the tongue is only connected to the rest of the liner near your toe kinda like the tongue on a shoe. you rely on the buckles to tighten the boot and secure your foot. with the kaos the liner has a nylon string that runs from the toe up to the top of the liner so you can tighten the liner like a high top to get a secure snug fit in addition to the buckles. if you go on the salomon web site and look and the blow up pic of the kaos or pro you can see the top of the cord just above the strap.
i have the kaos and if i don't tighten this cord then i can't get a very secure fit with just the two buckles. this gets more noticeable later cause the liners packed out A LOT from when i first bought them. i've seen other threads too about how much SPK liners pack out so it seems to be a normal thing.
there are also a couple of threads where people's cords have snapped but if you go through your local store or contact salomon you can get them replaced/fixed. i have been on mine for two seasons and haven't had a problem with that though.