The stiffest boot in the Vacuum Series is the Fischer RC4 130 intended for racer level skiers going as fast as they can, no matter the snow conditions. This boot has a 98mm last (but can be Vacuum Molded from 93-103mm) with a stiff 130 flex which provides the needed rebound and support aggressive skiers need from their boots. This boot also features Fischer's Vacuum Fit System where the liner AND the shell can be heat molded exactly to your feet. This procedure can be done at any Fischer Vacuum Dealer but it is not required. This boot can be skied right out of the box! The RC4 130 is a top notch boot for the expert skiers of the world, and at this price is a no-brainer.