An eri shin, kimono collar stiffening strip
Flexible mesh
An eri shin is a collar stiffening strip for a woman’s kimono. Women’s kimonos are worn with the collar edge folded inwards, in half, all the way down its length, and the collar is worn pulled down at the back of the neck; the younger the woman, the further down it is worn. The eri shin is placed inside the collar fold to make it firm and to hold its shape and help keep it in position
Made and bought in Japan
 
Condition:
Excellent - unused

Measurements approximately:
Eri shin are one-size-fits-all items