SRD:Negating (Armor Enhancement)
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Immediately after the wearer of this armor is hit with a magic weapon, the armor casts greater dispel magic on the weapon. (In the case of projectile weapons, the armor casts greater dispel magic on the weapon that fired the projectile if it is in range. If it is out of range, the armor does nothing.) No weapon can be affected by the armor more than once per day (regardless of the success of the dispel check).