See-Through Transparency Spray. Get See-Through Results! See the contents of sealed envelopes or manila folders - and never leave any telltale marks! No one will ever know you've used this remarkable investigative product. Won't damage the envelope or folder. Won't disturb the contents in any way. Won't cause the ink to run. See-Through is an excellent addition for crime scene forensics or for use in security facilities and correctional institutions. 200ML can.