Lighting Designers use these plastic filters to color stage scenery and to provide color correction for theatre, film, and television. Gel filters out unwanted color from the projected beam, allowing the chosen color to remain vivid. Gel can also change color temperature to enhance digital and film photography, while correcting lamp sources for better color balance. For short-term use, usually 6-10 hours. Apollo Gel Packs are convenient retail packs of popular filter colors. A Gel Pack contains twelve, 30 x 30 cm assorted color filter sheets inside a re-sealable plastic bag with sombrero cut hole for easy display and a colorful graphic slip sheet including gel tips and ideas.