Silver charm holder connector link.
Made in 925 Sterling Silver
I bought one of these a few years ago to add some of the charms I've picked up on my travels to existing chains.
I absolutely love mine and decided to introduce them to the store when I opened my Charm Archive.
21.5 x 6 x 1.5 mm
See here with garnet and lapis necklaces
Gold plated version is also available.