Gunmetal Rings #5: 7mm Split Rings (20/Pkg) will help you attach charms to your gunmetal chain. Some people also like them to match up with gunmetal lobster claws for bead-stringing projects on bead wire.

Note that split rings have some overlap -- there is more than 360 degrees. You can "wind" on charms or other findings much as you "wind" a key onto a key ring.

Look at the picture below to see a magnified picture of split rings.

Gunmetal Rings #5: 7mm Split Rings sell 20 pieces per package.