What is Supima Only the best cotton grown in America, with 35% longer fibers that feel smoother, take dye better and are 45% stronger than lesser cottons. It's rare, too. Less than 3% of American cotton is fine enough to wear the Supima name. So you know it makes for an exceptionally comfy and colorful robe. The one youll love first thing in the morning or while settling in at the end of your day. Supima is conscientiously sourced, American-grown cotton thats farmed to minimize environmental impact. The fibers are 50% longer than standard cotton, so yarns are stronger, softer, less prone to fraying or pilling, and hold color longer.