I saw this great thing
http://www.thingiverse.com/thing:3550

so I made the nine rings for the lanterns' corps !

all rings = 0.6inch

measure your finger size, change the scale with netfabb, export and print it !
for exemple :
your finger size = 1inch
change the scale factor to 1 / 0.6 = 1.66 and print it

I added a support into the ring, so print it without support material !

just cut it before using ;)