Small Clear Glass Wafers are flat on the back and have a slight indentation on the front side. These are thinner than the glass bubbles.  Artwork put underneath will not look as magnified. The wafer is lighter alternative to the glass bubbles.
All glass wafers will vary in size slightly. 
The small wafers are approximately 3/4" Round and 1/8" thick.
Set of 4

Match the wafer to our 3/4" glass to sandwich artwork between, wrap with copper foil tape and solder.