Hess samplers are used in similar circumstances to Surber Samplers (i.e. for sampling invertebrates from the substrate of slow flowing stream beds) but are more accurate as they have a sealed sampling system. The NHBS range includes three hess samplers, a large 300mm plastic hess sampler, a welded aluminium 145mm sampler and a 200mm economy sampler. The large and medium hess samplers have the option of added teeth, to improve the seal with the substrate and the large sampler has additional sections to extend the height upwards. There is a wide variety of mesh options available for upstream and downstream filters and nets.