Per 
Item #: SCP-XXXX
Object Class: Safe
Special Containment Procedures:
All instances of SCP-XXXX are to be cast into seperate blocks of concrete and are to remain seperated at all times. Instances of SCP-XXXX must be stored in rooms built of concrete walls, roofs, floors, and doors of at least 12 centimeters thickness or of comparable or higher strength. Should any two 2 instances come into contact with one another, all doors accessing the room are to be shut and locked immediately until all instances of SCP-XXXX have ceased movement.
Description:
SCP-XXXX-A to SCP-XXXX-U, collectively referred to as SCP-XXXX, are a set of 21 standard size billiard balls of unremarkable appearance. If any two instances of SCP-XXXX come into contact with each other, they will violently repulse, becoming capable of penetrating anything less resistant to impact than 9 cm of concrete, and will ricochet off of any surface strong enough to survive the impact.
The time necessary for each instance to stop moving has been measured to be approximately 14.3 minutes after the last collision with another instance. The number of colliding instances does not have an effect on this time, however, the actual time for all instances to stop varies dependent on the number of instances inside the room aswell as the rooms size, as the instances can collide in repeatedly while already in motion. The velocity of the objects once in motion does not appear to change over the course of this timespan, however, direct observation is made difficult by the unpredictable and destructive nature of SCP-XXXX.
SCP-XXXX was first aquired by the foundation in 19██ in an air raid bunker in ██████, United Kingdom, which had been converted into a night club. The precise details of the incident are unknown, however it is presumed that SCP-XXXX first started displaying anomalous behaviour that night, when two of its instances came into contact with one another during a game of billiard. 3 guests were killed by SCP-XXXX that evening, and every witness was administered amnesiacs. After Foundation personell arrived at the scene and witnesses were questioned prior to recieving amnesiacs, the balls were quickly determined to be the cause of the incident, and each was placed in a seperate case and transported off to Site 19, where they currently remain. After Incident XXXX-A, the decision was made to keep each instance in a cast of concrete to prevent any accidental activations in the future.
