Mylar is the most commonly used stencil material and the best material for most uses. It is tough flexible, cleanable, does not stretch, and can be used for many uses. We carry many grades 4 5, 6 7, 10 and 14 mil. A mil is one-thousandth of an inch. 4 and 5 mil is best for smaller projects and just a few uses Also particularly good for rounded surfaces. 10 mil is our most commonly used material with a good blend of durability and flexibility.