Non-woven belts are made of an abrasive impregnated nylon material that is often used for the scratch pattern it leaves. It leaves a very uniform scratch pattern typically used in applications where a satin finish is desired.
Keep in mind these recommendations are guidelines: the actual non-woven material is not officially rated in terms of grit. However, these recommendations match our (and customers experience) of what to expect.
Coarse: 40 to 60 grit
Medium: 80 to 120 grit
Very Fine: 150 to 180 grit
Ultrafine: 220 grit