Hardened Steel Shackle - Extra protection against hacksaw & cropping attacks. Close Shackle - Additional shackle protection to resist shackle attack. Double Ball Bearing Locking Mechanism - Extra strength to resist torsion & pull attacks. Chrome plated hardened steel body - Extra strength & resistance against corrosion. 5 pin cylinder with anti-pick mushroom pins - Extra protection against picking. Paracentric keyway - Extra protection against manipulation. 10 year guarantee.