Matched Set of Six 16GB, PC3-8500, DDR3-1066, 1066Mhz, 8.5GB/s Bandwidth, CAS 7-7-7-20, 5ns Cycle Time, ECC, Dual Rank, RoHS Certified, 512x72, 1.5V, 240pin DIMMs.This kit contains matched DIMM modules, which are specifically designed and SPD configured for the "Nehalem" and "Westmere" Mac Pro.These DIMMs include the Apple Thermal EPROM Sensor.These modules are compatible with the latest Apple Firmware.Configuration Information:The DDR3-1066 DIMMs for the Mac Pro require a Thermal Sensor for full performance and compatibility. Many 3rd party Mac Pro DIMMs do not include this sensor. MacMemory Net memory always conforms 100% to the Apple spec, and these DIMMs include the Apple thermal sensor. System Maximum: The system maximum in the 3rd Generation Mac Pro is 64GB (4x 16GB) in the 4-slot models, or 96GB (6x 16GB) in the 8-slot models. Tri-channel memory configuration gives a slight performance advantage. The DDR3-1066 DIMMs for the Mac Pro will run 1-3% faster if they are installed in matched sets of three or six modules (tri-channel). You may add DIMMs in any combination, but performance will suffer slightly if the DIMMs are not matched. Non-Mixable: These 16GB ECC DIMMs can ONLY be used with identical 8GB DIMMs from the same batch (i.e. ordered at the same time). You cannot mix these modules with other sizes of types of RAM in your Mac Pro.Matched Modules: The MacMemory Net kits for the Mac Pro DDR3-1066 contain a matched set of DIMMs. The kit will consist of identical brand/model/spec IC's. They will be from a single batch, and will have matching series numbers. This ensures maximum performance, and perfect compatibility.