SIDI ST Air BootsThe SIDI ST Boot features a hinged external support structure for helping to prevent lateral ankle movement while allowing for smooth fore and aft transitions on the bike. A set it and forget it cam lock closure system on the calf enables easy entry and accommodates a wide variety of calf diameters. All bolt-on components are replaceable.Features: Patented and trademarked Sidi Vertebra Systemprotects theachilles tendon Thermoplastic resin ankle protection Replaceable to sliders Composite inner sole Removable arch support Nylon shin deflector plate Perforated Lorica outer construction Double stitched in all high stress areas All bolt on parts are replaceable An elastic panel adjacent to the entry zipper allows a bind free zip and improved fit Dual compound sole DuPont polymer toe shift pad Perforated Teflon treated nylon lining Replaceable shock absorbing heel cup Padded achilles area External ankle support braces with closable air vents Cam-lock buckle system CE certified to EN13634:2017