HK Magnum series barrel condoms are the world's first barrel condom that effectively incorporates the essential allen tools to chrono your gun! We've taken a the original barrel condom design and enhanced it by created a sealable compartment that houses your set of chrono tools. The allen key sizes included are: 3/32 - 1/8 - 5/32 - 3/16. Now you can rest assured you'll never lose your tools again!