Expansion modules allow Cisco Nexus switches to be configured as cost-effective 10-Gigabit Ethernet switches and as I/O consolidation platforms with native Fibre Channel connectivity. N55-M16UP= is Nexus 5500 16-port Unified Port Expansion Module,it provides 16 1- or 10-Gigabit Ethernet and FCoE ports using SFP+ transceivers.This N55-M16UP= is similar with the N55-M16UP. The N55-M16UP= is a spare one.