SafePack
I use this to protect the game inserts on my Neo Geo AES video games. It works perfectly, cuts easily using a Dahle 508 trimmer. It's very transparent, you can hardly notice it's there. Highly recommended.
The other reviewer doesn't make sense - He ordered 4mil thick mylar and complained that it was exactly 4mil thick? I checked it with calipers at it is indeed 4 mil thick. I use it to make stencils, and it works PERFECT! It is not flimsy and is very crease resistant - which is excellent for what I use it for.
This is perfectly fine mylar. I use 0.4mm for jackets for books that don't have their own, and it works perfectly well. Some people like thicker mylar, some thinner, but to the point of the negative reviewer, I don't see how that is the fault of the product if you buy the wrong thickness for your needs.
This mylar is pretty, but the thickness is so great that it is VERY difficult to make precise folds. This is a good example of where more is not better. I went through two (very expensive) rolls of this stuff, and got terrible results. The tutorials on mylar you find online are all of people working with less thick mylar.