10 gauge vinyl

It sounds like you're trying to install a clear vinyl in a screen frame like they have on some porch enclosures. The size you want depends on the frame that you need to install the vinyl in. Do you have the existing spline that came out of the frame? That way you could match it up to the screen spline on the web site. 

If not, I would suggest ordering samples of a few different sizes to try out. There's no strict rubric on exactly what size works best on which window. At that point you will have to rely on good ol' trial and error. You can see our samples page here.