ECs are 10-12 inches long and 1 inch wide polyethylene tube. Thickness vary from 20 to 200 mikrometer. Since they ar not "standard" or quality controlled the same membrane can have zones of different thickness.
EC is low-density polyethelene semipermeable membrane (SPM). It is used to remove lipids from the samples in determination of organic compounds.
Read scientific article on dialysis with semipermeable membrane
