The pen is optimized for detection using the C-DiGit® Blot Scanner or the Odyssey® Fc Imaging System, and is suitable for use with film or other imaging systems. This unique marker delivers an ink which emits light when incubated with commonly-used chemiluminescent substrates, including WesternSure ECL and WesternSure PREMIUM. The ink is faintly visible for easy identification of marked membranes.