Ran across this stuff and have used for a few jobs and thought I'd share the 411. It's called "Accu Plot waterproof inkjet media" made by Chromaline 800-328-4261. (about a buck a sheet 8.5x11) have used the laser vellum crap, this is way better ... super opaque to burn screen, holds a fairly hard dot for halftones. Almost as good as a camera positive ... wouldn't use for a critical 4 color process job but...
NO I don't work for them and make no profit from posting this ... thoght I'd share (I've been looking for something like this a long time)
------------------ Designing... it's like an itch in the brain... an itch you can't scratch, that if you can figure out how to scratch it, it just itchs more