The boot is usually comprised of three components

Shell
The Shell envelopes the foot and provides support against the various forces while inversely acting as a transmitter of the us­ers inputs through first the binding and onto the ski.

Cuff
The upper cuff attaches to the shell and works like a lever to transmit forces from the skier’s leg to the shell enveloping the foot.
The way in which the cuff and shell are connected mimics the anatomical function of the ankle joint. This both supports ankle mobility while inversely bracing the skier to remain vertical on an inclined ski slope.

Liner
The liner is the soft textile link between the inner form created from the hard plastic cuff and shell and the users foot. It pro­vides the all important comfort, insulation and final support for the foot in the ski boot.