I use these sheet protectors in my classroom to make personal white boards for students they love writing on them. To make them you fill with two sheets of card stock and 1 layer of cardboard in between--this makes them thick. I use them especially to protect photos used for outdoor educational purposes they're a lot cheaper than laminating and protect my color photos from the elements and child hands. These sheet protectors are durable and reuse able. I recently used them to store and protect lessons and artifacts in my portfolio. All around excellent product!
As a teacher I have used them for years and am very pleased with the protection they offer. Great also for bulletin boards. I now also use them for pictures and put them in a binder.