The Sony FA-EP19 Eyepiece Cup acts as a replacement for the Sony A7S III Digital Camera's viewfinder.
It blocks the unnecessary light from entering the viewfinder to facilitate a detailed image observation.
The eyepiece cup is comfortable enough to use while observing the subject, even when you have the eyeglasses on.
Owing to the robust build, it protects the viewfinder from scratches, dust, and moisture.