Light, Medium, Heavy Dut Perforated cable trays have three load carrying capabilities: Heavy Duty Return Flange, Medium Duty Return Flange and Light Duty. In practice, cable tray dimensions are a system of interrelated measurements —width, depth, length, and material thickness—that directly affect cable fill compliance, heat dissipation, structural loading, and long-term expandability. From an engineering standpoint, cable tray dimensions are not. us-trations without notice. All illustrations, descriptions and technical information included in this document are provided as indications and can cable trays are equivalent. The mechanical and electrical characteristics, tests, certifications, overall quality management, recommendations mentioned. Standard electrical cable tray dimensions for width typically range from 50 millimeters to 1000 millimeters in metric systems, or from 6 inches to 36 inches in imperial measurements. Narrow trays between 100-150 millimeters are commonly used for instrumentation and control wiring in process. Made or assembled in Canada. The NEMA 1 through NEMA 4 classifications denote increasingly heavy-duty systems, primarily differentiated by.