This is a box of 100 sheets of 8.5 x 11" Write-On Film AF4300 from 3M. For educational and business purposes, this film can be used with an overhead projector for clear, on-the-fly lessons, charts and diagrams. They can be used with traditional transparency markers and washed when you're finished so they'll be ready for re-use. The clear material is acid-free and only a mere 4 mil thick. A real benefit of overhead transparencies is that you will never have to turn your back on your audience.