The Plankton Nets acc. to Apstein, used in limnological investigations, are manufactured in various shapes and sizes. The basic versions, intended for qualitative collections, comprise a stainless steel ring to which a conical net bag is attached. For easy retrieval the sample is concentrated inside a removable net bucket with sieve gauze covered side window. The standard mesh size of the Plankton Nets acc. to Apstein is 55 micron, which is used for the collection of phytoplankton.