The original leave-in spacer. Years of research led to a spacer that would react like a rubber spacer but be hollow, so it will stay in the joint and can be grouted over. Now the installer can grout a day earlier and not have to come back to remove the spacers before grouting. The Hollow Spacers will adjust up to 10% and not compress further and these spacers are longer to handle the radius corner tiles.
The 1/16" granite spacer is not hollow and must be removed.