The mostly natural category means that when the reclaimed fibers are labeled, they generally contain 70% or more of wool, cotton, silk, rayon or linen fibers. If they are not labeled then I burn test them to determine if they are natural. Where known, I will say in the description what the fibers are. If you need something to be wool free or acrylic free, please message me and I can let you know specifically, or I can make some that are from labeled fibers.