The Excalibur "Guardian" Anti-Dry-Fire system is designed to catch the string if accidentally fired without an arrow loaded in the crossbow. The Guardian(TM) Anti-Dry-Fire system is designed to catch the string should the crossbow be fired without an arrow loaded it also allows easy de-cocking. In the event the crossbow is fired without an arrow, the Guardian system, a self-contained unit housed inside the crossbow&&';;s scope mount, catches the string preventing the crossbow from dry firing, thereby preventing possible damage. It also features a built-in release so, at the end of your hunt,unlike with the other anti dry fire systems, you can easily de-cock your crossbow without having to fire an arrow, a major advantage. The Guardian system is standard on some Excalibur Matrix models and is available as an aftermarket part for all other Excalibur crossbow models. PRODUCT# 7016