It is the only mould-made paper that is sized on the machine and then additionally has an extra hit of sizing in an off-the-machine size bath. It is considered a hard-sized sheet to those who use it and consequently will take an enormous amount of surface abuse.
One can repeatedly rub-out, wash-out, and re-work an area without fear of the paper's surface-fiber lifting off or pilling. Because of its great internal strength, the paper can be soaked and stretched as desired.