Sleep Like Royalty! Dermatologists recommend silk pillowcases to help minimize wrinkles, dry skin, and bed hair. Silk is a natural material, great for sensitive skin. It offers the best sleep experience because it is a hypoallergenic, antimicrobial, and a highly breathable fabric. Momme (mm) is a measure of silk quality. 25 mm equals to durable, high quality silk. 25 mm is thicker than the 19 Momme silk found in other products, which is very lightweight and delicate, and will tear easily after a few uses. This pillowcase is definitely a must for anyone with curly hair or delicate skin! It is also a great gift that will be appreciated, cherished, and used for a long time. Purchase two so you can wash one and use the other.