Cisco 3945, SRE 900, PVDM3-64, UC and SEC License PAK bundle MEMGB= 2GB DRAM (1 DIMM) for Cisco ISR, Spare MEMGB= 1GB DRAM (1 DIMM) for Cisco ISR, Spare MEMMB= 512MB DRAM (1 DIMM) for Cisco ISR, Spare MEMGU2GB 1GB to 2GB DRAM Upgrade (1GB+1GB) for Cisco ISR MEMGB-DEF 1GB DRAM (512MB+512MB) for Cisco ISR (Default) MEMGU4GB 1GB to 4GB DRAM Upgrade (2GB+2GB) for Cisco ISR MEMGB-RF 2GB DRAM(1DIMM)for Cisc ISR,Spare REMANUFACTURED