Hardened Steel Shackle - Extra protection against hacksaw & cropping attacks. Double Bolted Locking Mechanism - Extra strength to resist torsion & pull attacks. Stainless Steel Body - Maximum 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.