What does 'momme' mean and what number should I look for?

Momme is a weight measure of silk density; higher generally means a thicker, more durable, more luxurious fabric. The widely cited sweet spot for pillowcases is 22 momme, with 25 momme options sitting at the premium end. Anything well below 19 momme tends to feel thinner and wear faster. Several picks here advertise 22–25 momme.