The slipsilk difference. Slipsilk is specially-commissioned and made to the exacting standards, developed and re-fined over ten years to provide the ultimate combination of shine, thickness, softness and durability. Slipsilk uses the highest grade (6A) long fiber mulberry silk, with a thickness of 22 momme Queen, Slip Silk Pillowcase, Silk Pillowcase, Pure Silk, Slip, Silk, Pillow Cases, Queen Size, Mulberry Silk