Kryptonite Evolution Series-4 1090 Integrated Chain Bicycle Lock Bike Lock (35.5") 10mm six-sided chain links made from 3T MANGANESE STEEL Patent-pending END LINK DESIGN secures chain to hardened deadbolt eliminating critical vulnerability HIGH SECURITY DISC-STYLE CYLINDER is pick and drill resistant Patented*, reinforced OVAL CROSSBAR LOCK HEAD SLIDING DUSTCOVER protects and extends cylinder life