TRABEM wrote:
Thanks John,

I did find metalized polypropylene caps in the Mouser catalog. Some
are quite expensive for no apparent reason and a few are inexpensive.
I still don't know why the big cost difference.

There were many pages of metalized polyester film caps, not sure if
they are ok or not. But, they are way cheaper, about half the price of
the lowest priced metalized polystyrene caps.

Are metalized polyester caps just as good as metalized polypropylene
caps?

Mylar caps are pretty good, but not as stable or as high @ as polystyrene.

You might read through this dielectric tutorial:
http://my.execpc.com/~endlr/film.html