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.

The double-ring construction not only avoids disturbances usually caused by the towing bridles fixed in front of the mouth opening of non-opening/non-closing plankton nets but it allows the investigator to work with two different mesh sizes at a time. Two 60 cm diameter stainless steel rings, connected by a coupling with rotatable connection point for the towing rope, are equipped with two 2.5 meter long net bags.