When sourcing a used mattress packing machine, you must prioritize mechanical integrity and compatibility. Key specs include the maximum compression ratio, which determines how much shipping volume you can save, and the sealing width, typically requiring at least 2500mm for king-size mattresses. Verify the PLC brand (e.g., Siemens or Mitsubishi) to ensure future software support and parts availability. Additionally, check the cycle time; a professional-grade machine should complete a wrap-and-compress cycle in under 45 seconds to maintain high throughput.