When you are considering a membrane sock
Sealskinz Runton Waterproof Cold Weather Mid Length with Hydrostop
The Runton combines three layers, an Aquasealz membrane and a merino-containing inner.
mid lengthnot specifiedWaterproof membrane
Keep in mind: Water can still enter over the cuff. Plan for cuff coverage and a spare dry pair; a membrane is not a substitute for either.