Scatter shield vs bellhousing

You can still find some ratty old Lakewood stuff out there. Unless it’s damaged, you can send it in for a new SFI sticker and have a window put in it for $450 plus shipping.

You’ll still have the cost of a new can in it, but it will have the window.
A couple of stupid questions. What is a window in a scatter shield and use? Who does this work and re certifying?