The Tecnica Mach 1 120 C.A.S. is a fantastic boot for expert skiers that have a medium to narrow foot and leg shape with a tall instep. Tecnica's i-Rebound Construction delivers a very high amount of rebound with each turn by having four metal to metal connection points between the upper cuff and the lower shell. A Quick Instep uses a softer plastic injection over the instep of the foot that allows you to enter and exit the boot very easily. The most unique feature of the Mach 1 120 is the C.A.S. (Custom Adaptive Shape) Liner that utilizes cork in the heel and ankle pockets that can be heated, punched, or ground down to get that perfect fit. Cork is used for it great insulating properties and a high amount of energy transmission. If you want power and rebound, in a boot that has a medium to narrow fit the Tecnica Mach 1 120 makes a great option. [+]