Buyers must prioritize durability and ergonomic design. Key specs include the IP Rating (typically IP65 or IP66) to ensure protection against dust and high-pressure water jets. The housing material should be high-impact, flame-retardant thermoplastic (ABS or Polycarbonate) or die-cast aluminum for heavy-duty environments. Additionally, verify the mechanical life of buttons, which should exceed 1 million operations, and ensure the rated insulation voltage (Ui) meets your machinery's electrical requirements (e.g., 600V).