OWC 32GB (2 x 16GB) PC10600 DDR3 ECC-R 1333MHz DIMMs Memory Compatible with Mac Pro Early 2009 & Late 2010 'Nehalem' & 'Westmere' Systems and Early 2009 Xserve. (OWC85MP3S9M032K) at Amazon.com
OWC 32.0GB (2X 16GB) PC10600 DDR3 ECC-R 1333MHz 240 Pin Memory Upgrade Compatible with Select 2009-2012 Mac Pro Models (OWC1333D3X9M032) at Amazon.com
OWC 16.0GB (2 x 8GB) PC3-10600 DDR3 ECC-R 1333MHz... at MacSales.com
Kingston ValueRAM 16GB 1333MHz DDR3 PC3-10666 ECC Reg CL9 DIMM DR x4 Server Memory KVR13R9D4/16 at Amazon.com