Hardened Steel Shackle - Extra protection against hacksaw & cropping attacks. Double Ball Bearing Locking Mechanism - Extra strength to resist torsion & pull attacks. Solid Brass Body encased in a Steel Jacket - Extra strength & resistance against corrosion. 5 pin cylinder with anti-pick mushroom pins - Extra protection against picking. Paracentric keyway - Extra protection against manipulation. Drill resistant keyway - Protects the cylinder against drill attack. 10 year guarantee.