What Makes Sea Island Cotton So Special? Its exceptional qualities begin with the fibre. Measuring up to 50mm in length, Sea Island cotton creates fabrics that are exceptionally smooth, breathable and remarkably durable. It is also the world’s rarest cotton, with only around 150 bales produced each year. For over a century, Sunspel has worked with this extraordinary fibre to create some of our most iconic T-shirts, polo shirts, knitwear and underwear, combining exceptional raw materials with generations of craftsmanship. Explore more at sunspel.com.