Machined from hot rolled steel or brass, the M II is sturdy and solid without becoming cumbersome. The metal is further protected with a metal oil and wax that prevents corrosion, along with the natural oils from your hands. Out of the box, the M II can comfortably fit up to five keys, but you can easily slide on a split key ring if you need additional space. The pin is machined from 1018 steel and finished with a blackening patina.