Fox's Spy Bolt  is an updated and improved version of the old Soviet KGB "dead drop" hollow bolt used during the Cold War. It features an O-ring seal for weather-proof storage of small valuables, communications, etc. It has reverse threading on the bolt head for additional security. 

Features & Benefits:

• Overall Length: 3.43"
• Maximum Depth: 2.81"
• Secret Storage Diameter: .49"
• Bolt Diameter: 3/4" 
• O-ring seal
• Weather proof storage