Momme (pronounced “mummy”) is a unit of weight used to measure and describe silk fabrics, usually expressed in momme weight (mm). The higher the momme, the heavier the fabric.GSM refers to grams per square meter of fabric.It is the major computation unit for fabric texture. 1mm=4.3g. Silk under 19 MM (10mm~16mm) is considered light weight, which is too thin thus not durable and is not recommeded. 19 MM is considered medium weight and anything above(22mm~40mm) that is considered heavy weight.