Well call me skeptical, but I have never seen the need for heat spreaders for the memory chips in my mac pro. It is common for performance memory for PC's to have heat spreaders built in. This is because PC systems are used by enthusiasts and high performance usually means high heat for the main components. The Mac Pro uses server grade memory (high quality with built in error checking), and this is usually not over clocked so heat spreaders are not usually needed. However, with the way I use my Mac Pro (lots of video converting and graphical work), the memory chips do run around 58-60 degrees. They arrived in a nice easy open blister package. Fitting was simple enough as they come pre-prepared with adhesive thermal tape on them. I stuck one on each side of my memory chips (some are single sided and some double sided). Re-inserted them in the Mac Pro and switched on. For comparison I only fitted the heat spreaders to two of my four chips. I ran up the system and started some transcoding (converting video files from one format to another). The results surprised me! The un-treated chips ran at 61 and 57 degrees, yet the fitted ones are holding steady at 44 degrees. Thats a HUGE difference in terms of temperature inside a computer that is very busy. Fitting the second set (so that all four memory chips were being cooled) resulted in even better performance. 40 degrees stable across all four DDR3-1333 ECC DIMM's! Overall I must say this is a quality product. Nicely packaged, easy to install and they do exactly what the packet says. 10/10 from me You can get these most from PC components shops, and amazon. Very pleased with these (and has spurred me into looking for a Northbridge cooler for the Mac Pro now, so I shall let you all know how it performs).