This is a gold filled chain double piercing connector with a tiny opal dangling from the middle (gold filled chain is different than gold plated in that the plating is much thicker making it higher quality and a more affordable alternative to real gold. It will never peel off the way gold plated jewelry does. with proper care it can last as long as real gold.). To measure for your chain, please use millimeters which are the little lines between centimeters for a more exact fit. For example, 2 centimeters is 20 millimeters, 2.5 centimeters is 25 millimeters, 3 centimeters is 30 millimeters, and so on. Measure from the inside edge of one piercing to the inside edge of the other as shown in the photo. If you are only able to measure in inches that is is also fine.