All Elfbeads glass beads are made with the highest quality glass, sourced from all over the world. All Elfbeads beads have a silver core with a 5 mm hole that fits all European bead brands. Elfbeads cores are marked with E925. This logo stands for Elfbeads and sterling silver925. If you want to be sure if your bead is an original Elfbeads, you can check the logo in the core.