When evaluating shower mixer taps, prioritize solid brass construction (H59/H62 grade) for the body to ensure corrosion resistance and longevity. The valve core is the most critical component; ensure the supplier uses ceramic disc cartridges (preferably brands like Sedal or Kerox) which are tested for 500,000 to 1,000,000 life cycles to prevent leaks. Additionally, check the plating thickness, typically requiring a nickel layer of ≥8μm and a chrome layer of ≥0.25μm to pass a 24-hour or 48-hour Acid Salt Spray Test (ASS).