The knot density in a Heriz rug like this heriz azerbaijan antique oriental area rug 7×9 ranges from about 40kpi to about 100kpi. (Although occasionally finer knotting silk Heriz carpets were manufactured.) The coarser knotting enhances the looser designs and styles of these carpets. Heriz (Heris) style rugs are typically larger, more durable, and more resistant. The knotted wool yarn pile on a cotton warp makes this possible.