IEC 61537 is the internationally recognized benchmark for metal cable tray systems. It applies to cable trays made of steel, stainless steel, aluminum, or other metallic materials. Whether you're designing a new. OBO BETTERMANN has offered prod-ucts and solutions for electrical instal-lation for over 100 years. With our many years of experience, we are one of the leading manufacturers in this field. Please make sure. What is the allowable deviation of the national standard for the thickness of cable tray? The thickness of the trough cable tray includes the pallet thickness, the cover plate thickness and the connecting plate thickness.