Dec 21, 2021 · The M1 (0.1 micron) is a low flow type membrane suitable for most liquids and the M2 (0.8 micron) is a high flow type recommended for higher surface tension liquids. Our Oleophobic membranes designated by the “H” suffix (i.e. MT.33.M2H) have an extra thin layer which repels hydrocarbons and will block both water and hydrocarbons.