16"-never restricts your neck to take deep breaths. 18"-referred to as princess piece-these knickknacks are designed to sit down on the clavicle. 20"-Siting slightly below the clavicle-is termed a matinée & sometimes the standard length for adding lockets & pendants. 22"-Landing at the highest of the bust-this falls into the matinée class. 24"-this long ought to be at the middle of the bust or below it.