The ultimate disc lock. XENA's top of the line mega-strong XN18 features an 18mm high-security four-way locking pin, reinforced carbide substructure and a fortified key barrel with carbide underpinning. The XN18's mono-block construction body and locking pin are made entirely of the finest grade high nickel-content stainless steel. Shock & motion sensors trigger a 110 dB alarm. The unit is self-arming, with no on-off switch, and re-sets automatically to armed mode within 15 seconds if the disturbance stops. Combined with the Claw18 and XC chain it makes a virtually impenetrable lock and chain set-up. It even features a Blue LED indicator light to warn that it is armed and means business.