Part Number: 00D4959-AXA (Axiom ibm supported 8gb module #) Part Number: 00D4961-AM (Addon 8gb ddr3-1600mhz dr udimm ) Part Number: 00D4964 (No description) Part Number: 00D4967-AM (Addon 16gb ddr3-1600mhz dr rdimm) Part Number: 00D4968 (No description) Part Number: 00D4968-AM (Addon 16gb ddr3-1600mhz dr rdimm) Part Number: 00D4968-AX (Axiom 16gb ddr3-1600 ecc rdimm f) Part Number: 00D4968-AXA (Axiom ibm supported 16gb module ) Part Number: 00D4970 (Memory,16gb 1x16gb 2rx4 pc3-1280) Part Number: 00D4970-AM (Addon 16gb ddr3-1600mhz dr rdimm) Part Number: 00D4980-AM (Addon 8gb ddr3-1333mhz sr rdimm ) Part Number: 00D4981 (No description) Part Number: 00D4981-AM (Addon 8gb ddr3-1333mhz sr rdimm ) Part Number: 00D4981-AX (Axiom 8gb ddr3-1333 ecc low volt)