When sourcing a 3m duplex mast, you must prioritize structural integrity and lifting efficiency. Key specs include the collapsed height (overall lowered height) to ensure it clears doorways, and the rated load capacity at full extension. Look for masts constructed from high-strength rolled steel channels to prevent twisting under load. Additionally, verify the cylinder seal quality (e.g., NOK seals) to prevent hydraulic leaks and ensure smooth mast rails with heavy-duty rollers for reduced friction.