I have several of these units.  All items are used and in good working order.  Price is per each optimizer.  Order as many as you would like.

If you have any questions please feel free to ask.  

Spec details from manufacturer. Note additional specs in one of the photos: 

- Max output wattage: 350W

- Max input voltage: 60V DC

PV Power Optimization at the module-level

• Up to 25% more energy
• Mitigates all types of module mismatch losses, from manufacturing tolerance to partial shading
• Flexible system design for maximum space utilization
• Next generation maintenance with module-level monitoring
• Module-level voltage shutdown for installer and firefighter safety