The peekaboo's cover only the interior
lens, glass, whatever. For most portlights
these are standard sizes. However, the company also custom makes the wee rascals. Give them the dimensions or a template and they will accomodate you.
They are a plastic material that have opaque vertical stripes imbedded. Two pieces, one inboard and the other outboard
are capable of sliding about one half inch, the thickness of the stripe. When slid together the whole arrangement is more or less opaque, slid the other direction they let the light in.
The only problem I've had is that they are held to the window by velcro tabs. The adhesive
on the tabs is not the greatest when subject to the heat that a closed boat can accumulate. Sooo, when the first tabs started to pop off, a drop of contact cement to replace the expired adhesive
took care of that. Right now, I'd say they are about 5 years old and going strong.