I bought this to match an anklet that looks just like this as a set for my birthday.  Anklet fits true to size, this is by NO MEANS an 18" necklace.  You can't even attach an extender bought separately because it does not have a clasp closure, but rather a screw together closure.  It fits my 9 year old like it should fit me.  Oh well.  We'll see how it holds up.  Super cute otherwise.