The Pluronic PE types are low-foaming, nonionic surfactants. They are block copolymers in which the central polypropylene glycol group is flanked by two polyethylene glycol groups. The Pluronic PE types are designated by a four-figure or five-figure number. The first digit – or first two digits – is a guide to the molar mass of the hydrophobe, in this case polypropylene glycol, on a scale of 1 –10. The second, or third, digit is the percentage of polyethylene glycol in the molecule, divided by ten.