Supermicro Sliding 2U-3U Rack Mount Outer Rails MCP-290-00053-0N Non-Rev B | eBay
These rails are version A or non-Rev B. For an excellent discussion on the different versions of Supermicro’s rail kits, see Art of the Server’s Youtube video “How to buy used Supermicro rack rail kits for your Supermicro server.”.
www.ebay.com
Looks like a pretty good deal if you've got spare inner rails lying around.
