It is mainly used for alpine or downhill skiing and is also known as downhill ski boots. Both toe and heel of the boot is secured and the heel will be always locked down. In order to firmly hold foot and ankle a stiff plastic shell is designed that gives the control of the skis. The stiffer the boot, better control and precision while skiing is obtained. The alpine ski boots should be of the right size else the skier may lose control. The liners protect from cold and absorb vibration. Since alpine skiing requires easier turns, the pivot point near the ankle allows the upper shell to slightly flex forward.
Alpine ski boots are divided into four categories:
Piste boots which are used for regular skiing and walking which are heavier and stiff.
Race boots are stiff, tight and not as comfortable as the others and are mainly focused on performance.
Freeride boots are lightweight and have grippy soles. Since it deals with mixed terrain and has to adapt to sudden changes, it has stiff lateral flex.
Freestyle boots are more flexible than other boots because they should easily adapt to different jumping styles.
They have almost similar features to that of alpine ski boots except the bellows which are at the forefoot which helps for the telemark turn. It may become looser and the toes may not hit the front portion.
They have features of both alpine and telemark ski boots. It has both walk mode for ascents or toggle mode for flat surfaces which can be turned on when required. A rubber outsole is fitted for traction and the heels can be locked or unlocked descending and ascending respectively. The touring bindings hinge at the toe while hiking and lock down for mountain touring.
The tech/AT/Pin bindings are used for ski touring which are very light without a releasing mechanism.
The Frame bindings are heavier and are mainly used for alpine boots allowing ski touring.