Silk Dreams pure silk pillowcases are a 22 momme weight of silk. This is heavier than most pillowcases on the market, which is either 16 momme or 19 momme, and the superior grade means they are more lustrous, more durable, and machine-washable. Silk Dreams silk pillowcases come with a practical zipper on the side to keep your pillow in place all night. Not only do you get these benefits whilst you sleep, but you also benefit from the unsurpassable feeling of pure luxury as you sink into silk to sleep!