This item is provided by Crutchfield.com and includes free phone technical support for the life of the product. Details on how to take advantage of this service will be included with your package. Should you have any issues locating information on how to contact Crutchfield Technical Support, please contact this website's Customer Service department. Stack on some more storage The Salamander Designs Synergy System extender lets you add more shelving onto select Synergy System cabinets . It features anodized aluminum posts that attach firmly to the tops of your cabinet's posts. The extender can support up to 350 lbs. on its top shelf, and 75 lbs. on each of its three lower adjustable shelves. Note: This extender is not designed to be used as a stand-alone cabinet. What's in the Box: 1. Top shelf 2. 3 Rear-panels 3. 3 Adjustable shelves 4. 8 Posts 5. 8 Connectors 6. 12 Shelf-pins 7. Assembly Instructions