Today we have added Complete dual CPU core processor trays featuring Two Quad Core CPU's  for the Mac Pro 2010 version 5,1.  These are a great upgrade to any 5,1 quad core Mac Pro.

Dual CPU Trays can be found here 

The Mac Pro 5,1 uses lidded CPU's so changing processors is not as complicated as the Mac Pro 4,1.

This Tray will not work properly in a Mac Pro 4,1 even with the 5,1 firmware update applied.  Fans will run full speed all the time.