Premium Flouro-Carbon Treated - White is a Urethane Grade, 99% holdout material.  It is a bleached Kraft Paper that is chemically treated for hold out.  This white Kraft Paper is much stronger than anything that Automotive Refinish is accustomed to using.  It has extremely good bleed through resistance and superior flexibility.  It conforms to curves better than any of the traditional materials.  Premium Quality Paint Shops use this higher grade masking material because it is stronger, more flexible & eliminates paint bleed through, thus cutting down on the detail clean-up work necessary with lesser quality materials.