When sourcing marble drill bits, the most critical factor is the tip material. For marble, which is a relatively soft but abrasive natural stone, Vacuum Brazed Diamond or Electroplated Diamond tips are superior to standard carbide. You must verify the diamond grit size; a grit of 40/50 or 50/60 is ideal for a balance between cutting speed and finish quality. Additionally, ensure the shank type (e.g., Hex, Round, or M14 thread for angle grinders) matches your buyers' equipment to avoid compatibility issues.