These no-wire racks will not rust or stain and have been designed so that the flow over the length is uninterrupted except by the test tubes containing samples. A high specific gravity plastic has been chosen to provide excellent stability with no tendency to float or move in circulating water baths. An alpha-numeric grid reference on the top tier enables precise location in the rack of particular samples. Shipped flat, easily and permanently snapped together to save shipping expense and reduce shelf space needed in storerooms.