The custom of wearing neck rings is related to an ideal of beauty: an elongated neck. Neck rings push the clavicle and ribs down. The neck stretching is mostly illusory: the weight of the rings twists the collarbone 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.
The custom requires that the girls who wear the neck rings start before puberty, in order to get the body used to them. These heavy coils can weigh as much as 11 pounds (5 kg).
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 clavicles (collarbone) to cause them to deform and create an impression of a longer neck.
Small Kayan girls may wear brass collars from the age of two to five years old, as it is more comfortable to deform the collarbone and upper ribs slowly. The alternative, an accelerated process at around the age of twelve, when girls first begin to compete for the attention of boys, is painful. Marco Polo first described the practice to Western culture in c. 1300. Refugee practitioners in Thailand were first accessible to tourists in 1984.