Optic Shop Pro-Moisture Chamber With Elastic Head Band - Size Large

Looking for patch that can be worn with glasses. Is this flat or concave as most seem to be?

Is this path for either eye or must it be ordered left or right?

How do you measure (where to where) to decide small or large?

Is the clear vinyl part hard cinyl or soft? I need a hard clear shield to keep me from rubbing the eye in my sleep.