Water Rings were metallic counters that represented the volume of water released by a body of a dead Fremen processed through a deathstill. They were manufactured in denominations ranging from 50 liters to 1/32 of a drachm (a drachm being 1/150 of a liter).
The water was stored in the sietch holding basin, but possession of the rings gave permission to draw upon it at need, or bestow it upon needier members of the tribe.
The body of one killed in a personal combat was processed and the rings representing this water were given over to individual members of a tribe: they-and possession of the water they measured-were the property of the combat's victor for compensation for the water lost during the fight. Fremen women who killed an (outside) enemy, the combat water and its rings were turned over, to the tribe's Reverend Mother and were believed to confer Shai-Hulud's special blessing on their donor.
The rings possessed great social significance above and beyond their representation of water. In Fremen betrothal, the would-be groom presented his water rings to his fiancee, she would then arrange them on fine wires to be worn either as earrings or (more commonly) as hair ornaments. Part of the marriage ceremony involved the groom's patting the newly fashioned ornaments on the bride.
This use of the water counters helped regulate much of the interaction between the sexes since it helped to control the polygamy permitted to Fremen males. It was not permitted, for example, for men to divide their counters between two or more women, so multiple marriages did not take place. If a man wished to take another wife, he had to wait until he had accumulated more rings; and any Fremen suspected of inviting challenge solely for that purpose was considered ridiculous and made the laughingstock of his tribe.
Following the death of their owner, water rings were returned to the tribal store, or, if worn by a woman, remained with her until her death.