BeautySpaceNK Slip Pure Silk 360 Thread Count Silver Silk Pillow Case King Slip is the #1 preferred brand of silk pillowcases softness and durability. ANTI AGING: We spend a third of our lives in bed. In laboratory testing Slip silk pillowcases so they can help keep your skins moisture and valuable face and hair products where they belong on your face and hair. Slip silk was also shown to create 43% less friction on average which can reduce stretching and tugging on delicate facial skin.