Maximum Security The ultimate disc lock: The 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. Mono-block construction body and locking pin are made entirely of the finest grade high nickel-content stainless steel. Alarm: Shock & motion sensors trigger a 110dB alarm. The unit is self-arming, with no on-off switch, and re-sets to armed mode within 15 seconds if the disturbance stops. Unique features include a Blue LED indicator light to warn that the XN18 is armed and means business.Combined with the Claw18 and XC 14mm chain, the XN18 makes the highest security level lock and chain set-up in the XENA arsenal.