SLEEP MASK BLACK. Features: 100% pure silk filler and internal liner. Includes slipsilk covered elastic band. Made from 100% highest grade (6A) long fiber mulberry silk with a thickness of 22 momme. Non-toxic dyes. Research Results: Slip pure silk products are made using slipsilk, developed and refined for over ten years to provide the ultimate combination of shine, thickness, softness and durability. In laboratory testing, slipsilk was shown to create 43% less friction, on average, versus cotton pillowcases*. *Compared to widely available cotton pillowcases with a 220-360 thread count. :