Constructed of Lorica and is lined with Teflon vented mesh. Only Sidi goes to trouble and expense of creating a multiple liner boot system in its racing boots. Lorica® is a composite micro fiber material created from strands that are so fine, each one is less than one thousandth the thickness of silk. When injected with special resins, these fibers act like natural leather skin, but with the addition of better strength, softer texture, lighter weight and better moisture protection. Sidi has added a small elastic panel to aid in a smooth zipper operation as it allows a bit of movement via the elastic as the zipper passes over the rider’s ankle ball. The rear upper part of the boot is made up of the following mechanisms: The Tecno Calf Tensioner mechanism adjusts the leg circumference. Placed in the back of the boots upper, it works through a nylon wire that hooks directly to the shin plate. The Tecno Shin Tensioner mechanism helps the Tecno Calf Tensioner close the leg upper on the front part of the boot. The two lateral nylon braces join the ankle joint with two screws that are protected by nylon caps. This system is reinforced with fiberglass, supports the ankle and is easy to replace. This system allows excellent flex movement front-to-back while being firm side-to-side. Tecno Instep Tensioner, a fastening system on the front part of the foot, on the instep. Shock Absorbing Heel Cup. Non-vented. Shin Plate. Gear Change Pad. Vortice Slider: toe slider is made in nylon reinforced with fiberglass. It is fitted with a new air intake and an innovative alloy insert. Racing SRS Sole: all new sole is constructed of a polyurethane and rubber blend.