The result is a perfect fit and maximum transmission of energy from your foot to your ski. Progressive Flex for better rebound. Carbon Steel Cuff Rear Plate and Buckles: the tempered plate positioned at the rear of the cuff stiffens the rear, increasing transmission of power when leg is flexed. The Delta Force Plus device is a special cylinder that can customise the boot flex, regardless of outside temperature. This allows you to choose from 2 different settings. Standard setting is harder flex and Extra setting is softer flex. Also features the ComfortFit liner, Canting and 35mm Velcro Strap.