Extra thick 16 mm case hardened kryptonium steel shackle resists cutters and leverage attacks cross bar is shielded by a hardened kryptonium steel sleeve in a double crossbar design for double security high security anti pick disc style cylinder with patented double deadbolt lock flat key with integrated sliding dust cover protects the cylinder the transit flexframe u mounts quickly and easily and supports the transportation of the most common u lock sizes the flex frame u fits bicycle frame tub