With guidance from John Gannon of the Great Lakes Lab in Windsor, Ontario, Wildlife Supply (TM) has developed the definitive low-cost apparatus for enumerating zooplankton micro-crustacea. It is the perfect size to hold a large volume of sample - about 39 ml, in fact. The shape and configuration of the shallow, etched groove (1/2" deep and 3/8" thick) help locate specific areas on the chamber. A compact 3-1/2" by 4-1/2" in size, it slips easily under a dissecting microscope. Straight sides mean you don't have to focus up and down. Rounded edges prevent specimens from catching. It is so outstanding, in fact, that our Aquatic Biologist's one regret is that her lab never had one.