Kingston 16 GB Kit (4 x 4 GB Modules) 1066MHz DDR3 DIMM Desktop Memory With Thermal Sensor For Select Mac Pro's KTA-MP1066K4/16G Four 4GB modules of 1066MHz DDR3 Desktop Memory Specifically designed and tested for compatibility 240-pin unbuffered DIMM From the industry leader in PC memory Backed by a lifetime warranty and free technical support