When selecting rubber cables, you must prioritize conductor material, insulation type, and voltage rating. Ensure the conductor is 99.9% oxygen-free copper for optimal conductivity. For insulation, EPR (Ethylene Propylene Rubber) is preferred for its excellent thermal properties, while the outer sheath should be CPE (Chlorinated Polyethylene) or Neoprene to provide resistance against oil, chemicals, and UV radiation. Always verify that the voltage rating (e.g., 450/750V or 0.6/1kV) aligns with your specific machinery requirements.