Hide those precious or secret items! With this real 3/4″ machine bolt, you can keep your stuff hidden away. Roll up a secret note, hide precious gems, a memory card, or some extra cash. The storage compartment has a diameter of .49″ and a depth of 2.7″. Perfect gift for any guy who ever dreamt of espionage. This bolt is inspired by the Soviet KGB “dead drop” hollow bolt used during the Cold War. Now that is exciting.