14k gold-filled is a USA industry standard that legally requires 1/20th, or 5% pure gold by weight. It's a strictly regulated process that involves pressure bonding multiple layers of solid 14k gold with extreme heat over a core of brass, resulting in a durable, quality, real gold product. It tends to have a warmer tone than solid gold after heating. It can sometimes result in exposure of the base metal at solder seams which can discolor skin temporarily, similar to the effect of wearing copper or brass jewelry. However, all 14k gold-filled earring wires used in my jewelry will never have this issue, as they are not heated, thus they can be worn by people with metal sensitives who can wear solid gold.14k gold-filled metal is very high-quality and is much more durable than gold vermeil or plate - it won’t rub off easily with wear like those lower quality materials will and it is said to have a life span of 30+ years (i.e., before the 14k gold layer is worn away) with normal wear.