When procuring three-phase meter boxes, the material composition is paramount. You should prioritize SMC (Sheet Moulding Compound) or polycarbonate (PC) for their superior insulation, corrosion resistance, and UV protection, especially for outdoor installations. Ensure the box has an IP65 or IP66 rating to guarantee protection against dust and high-pressure water jets. Additionally, verify the rated voltage (typically 380V/400V/415V) and current capacity to ensure compatibility with the local power grid and the specific industrial or residential load requirements.