The durability of a dumbbell handle depends heavily on its base material and surface treatment. You should prioritize Solid Steel (A3 or 45# carbon steel) for standard use, or Stainless Steel for high-end, corrosion-resistant requirements. Ensure the surface is finished with High-Quality Chrome Plating or Black Manganese/Zinc coating to prevent rust. For the grip, look for Precision Knurling with a depth of 0.25mm to 0.5mm to ensure a secure, non-slip grip without being overly abrasive to the skin.