These end caps are hand carved from resin with swirling colors of rust, silver, and caramel. These end caps are stunning. The colors are vibrant and dynamic. The pair pictured have a 12mm opening, but this item is available in virtually any size. If you need a size not listed here, just let us know - we can make it. Each end cap is approximately 3/4 inch long. The magnet is a rare earth magnet and is quite strong. It will securely hold a necklace or bracelet.