Instruction: Generate an answer to the question by utilizing the information contained in the document.

Input:
Question: I have a MacPro4,1, Quad-Core Intel Xeon, 2.26 GHz6GB Ram of (DDR3 ECC 1066MHz) - Would it work to replace my current RAM with your 16GB set? Thanks
Document: I put it in and rebooted and my Mac Pro mid 2010 2 x 2.4 Quad-Core Intel Xeon recognized it. All is well...You'll want to be sure you follow the recommended order of of inserting the memory into the slots, especially if you're mixing it with other memory sticks.
I upgraded my Early 2009 Mac Pro to the new Maverick OS and it slowed down my computer so badly that I almost replaced it thinking the 2009 model wasn't fast enough for today's technologies. I installed the 16GB of RAM and now my computer is lightening fast. I am a photographer often running Photoshop, Lightroom and Indesign among other programs at the same time and my computer now handles it with no problems. I highly recommended upgrading your RAM first before buying a new computer.
My computer was so slow I could barely function. I bought 32gigs of ram and I can now run several programs at one time without any problem! I am a editor so I can render in Final Cut while exporting in After Effects with no issues now.
I bought this memory to help boost the speed of a 2009 Mac Pro. Installation was easy. Mac Pro isn't running any faster, unfortunately, but that has everything to do with the fact that it's an overpriced clunker and nothing to do with the memory. Why anyone would buy a Mac is beyond me. I inherited this crap box and have been trying to get it up to speed with my PC. Enought ranting. You need memory? You can't go wrong with OWC.
My Mac Pro worked great with 8 Gb of RAM, but it was amazing how much faster it is with the 16 Gb RAM bought at a very good price.
Answer: Yes, it will.