mm is momme, simply, we write 19mm, 22mm etc.
momme is Silk fabric quality, about silk fabric weight, about silk fabric thicker. More higher momme, more thicker, more durable, more yarns be used, more higher price.
1momme = 4.3056g/m2
16mm = 68.9g for 1m2
19mm = 81.8g for 1m2.
22mm = 94.7g for 1m2
25mm = 107.6g for 1m2
30mm = 129g for 1m2