It's not a $600 Diablo Flame boot but if you want a little more flex with some high-end performance features Tecnica's Diablo Spark Ski Boot is a smart and practical choice. While the Diablo Spark's SuperFit liner doesn't have the same versatile customization features found boots with an UltraFit liner it does offer the Twin Support System along the upper cuff that's available on all of Tecnica's top-end performance boots. The Twin Support System has extended upper flaps that help distribute lateral pressure creating a closer closure around your shin for a responsive performance. By kicking up the response and dropping the flex to 70 the Diablo Spark offers a tantalizing balance that will appeal to advanced and expert skiers who want boot comfort for extended ski days. All Tecnica Diablo ski boots have a a triple-density construction that places the most rigid material around the heel toe and toe box and the softest flexible components around the top of the insteps. The Diablo Spark UltraFit Ski Boot has a similar performance fit as stiffer Diablo boots with an advanced boot last that features lower volume in the heel ankle and leg regions while cranking up the volume in the forefoot and asymmetrical toe box. Tecnica's hinged Rapid Access opening along the upper cuff of the Twin Support System offers a stronger sleeker hinge for improved closure. The result is a boot that harmonizes the energy from your foot with your binding interface and ski. The thermoformable pre-molded EVA SuperFit liner has a soft external ethafoam exterior with slow memory that conforms better to the shell than some competitor ski boots. If you love the power and strength potential of the Diablo line but you want a little more flex to ski throughout the day the Diablo Spark is a great way to go down any side of the mountain.