Cisco 16-Port 10 Gigabit Ethernet Fiber Module with DFC4 - Expansion module - 10 Gigabit X2 x 16 - refurbished - for P/N: WS-C6503-E-RF/ WS-C6506-E-RF/ WS-C6509-V-E/ WS-C6509-V-E-RF/ WS-C6513-E