"For a ring to be resized, it needs to be made of a metal that a jeweler can work with, such as silver, gold, or platinum," says Gandia.
"There also needs to be enough room on the ring for the actual work to be done."
If your sparkler is set in a full eternity band, it can't really be resized. Because the stones are set all the way around the band, there's no bare metal to work with.
Type of Rings That Can Be Resized