This SAE Recommended Practice provides general guidelines on the material selection, construction, and qualification of components and wiring systems used to construct nominal 12 VDC and/or 24 VDC electrical wiring systems for heavy-duty vehicles The guidelines are limited to nominal 12 VDC and/or 24 VDC primary wiring systems and includes cable sizes American Wire Gage 20 to AWG 4 on heavy-duty on-highway trucks. The document identifies appropriate operating performances requirements. This document excludes the male-to-female connection of the SAE J560 connectors.