Neck rings are formed with one or more spiral metal coils of many turns worn as an ornament around the neck of an individual. In a few African and Asian cultures neck rings are worn usually to create the appearance that the neck has been stretched. Padaung (Kayan Lahwi) women of the Kayan people begin to wear neck coils from as young as age two. The length of the coil is gradually increased to as much as twenty turns. The weight of the coils will eventually place sufficient pressure on the shoulder blade to cause it to deform and create an impression of a longer neck.
The custom of wearing neck rings is related to an ideal of beauty: an elongated neck. Neck rings push the collarbone and ribs down. The neck stretching is mostly illusory: the weight of the rings twists the collar bone and eventually the upper ribs at an angle 45 degrees lower than what is natural, causing the illusion of an elongated neck. The vertebrae do not elongate, though the space between them may increase as the intervertebral discs absorb liquid.- wikipedia.com
Another bizarre exhibit at Believe it or Not Odditorium. Women of the Padaung tribe in Burma wear heavy brass rings around their necks.