art supply question/ for comics?

Question

For greyscale shading in comics they use these sheets of film with different values. They usually use it for Manga type comics. I need to get some but I can't rember the name of the stuff. Please tell me what it's called.
Thank you.

Answer 1

Letraset Screen tones should do the job, you need to have a scalpel as well. to cut the edges into the shape you want. I'll give you the link below =] Good Luck!

Answer 2

Zipatone.