The Kayan are a sub-group of the Red Karen (Karenni) people, a Tibeto-Burman ethnic minority of Burma. Women of the various Kayan tribes identify themselves by their different form of dress, the Kayan Lahwi tribe being well known for wearing these neck rings, brass coils that are placed around the neck, appearing to lengthen it. Girls first start to wear rings when they are around five years old and over the years the coil is replaced by a longer one with more turns. The weight of the brass pushes the collar bone down and compresses the rib cage. The neck itself is not lengthened; the appearance of a stretched neck is created by the deformation of the clavicle.
A wonderful response to my Q of monks - thank you. P/Ms sent.