G.SKILL Ripjaws X Series 16GB (4 x 4GB) DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9Q-16GBXL - Newegg.com
CMS 16GB (4X4GB) DDR3 10600 1333MHZ ECC Non Registered DIMM Memory Ram Upgrade Compatible with HP/Compaq® Workstation Z820 1333Mhz Ecc Unbuff for Server Only - B126 at Amazon.com