18k gold plated. 18k gold contains 75% pure gold and 25% other metals, thus making it a higher quality of gold compared to 14k (which contains only 58% pure gold. The chain is adjustable. Our jewelry is skin-friendly and appropriate for sensitive skin. The high-quality materials and craftsmanship of the pieces mean they will not corrode or irritate the skin, ensuring they can be worn on a day-to-day basis without issues.