Acrylic or Glass cabochon eyes. They have a following effect once eyelids are added to them!
Acrylic can have LED's installed into them, glass cannot! *Glass may have small scratches from the factory, I pick out the unusable blanks from the stock but minor imperfections happen with them as they're shipped from China.
1-1/4"/31.75mm Diameter (Size I use for smaller eyes).
1-1/2"/38.1mm Diameter (Size I usually make).
2"/50.8mm Diameter (Very large, good for more toony suits with a foam base).