Based on the design of California Cooperative Oceanic Fisheries Investigations (CalCOFI), the Ring Trawl Net today is the standard non-opening/non-closing plankton net for quantitative sampling of larger volumes of water during horizontal or oblique tows. The 100 cm diameter stainless steel ring, equipped with a 4 meter long net bag should be operated in conjunction with a 22 kg V-Fin depressor to create negative lift at the instrument.

For easy retrieval the sample is concentrated inside a removable plastic net bucket with side window (covered with sieve gauze). A Mechanical Flow Meter can be fixed in the net to measure the filtered water volume.