Crucial 8GB Single DDR3/DDR3L

I replaced an older iMac with a Late 2013 27" iMac (3.2 GHz i7, GTX 780M 4GB, 1.28TB Fusion Drive) with 16GB of RAM in November. I planned on upgrading to the max 32GB of RAM at a later date. I held off upgrading due to mixed messages about the differences between the Crucial RAM Amazon was selling here and the recommended RAM on Crucial's website (which was more expensive). It seems like the dust had settled so I ordered two individual 8GB modules since the price was slightly less than the two-pack package at the time. Although I had concerns about fit, etc., my main concern was voltage requirements since higher voltage generally means more heat; heat being an enemy of electronics, particularly computer components. My understanding is that my particular model of iMac employs 1.35v RAM. Crucial's website specifically states that their recommend RAM is 1.35v. The Crucial RAM Amazon sells here is listed as 1.35v/1.5v. Just prior to ordering I contacted Crucial directly to be sure the RAM Amazon was selling was compatible with my model of iMac. MY EMAIL TO CRUCIAL: "Hello, Can you please tell me what the difference is between Crucial Part Number CT4951624 and Crucial Part Number CT2K8G3S160BM? Specifically I want to buy a 1.35v model. Part Number CT2K8G3S160BM is listed as 1.35V/1.5V. Thank you very much!" CRUCIAL'S REPLY: "Thank you for contacting Crucial. I have looked at both of the part numbers you sent in your email, and these are actually the same. The difference between the number CT4951624 and CT2K8G3S160BM is that the smaller one tells us that CT2K8G3S160BM is guaranteed compatible with your specific system. The longer part number, is considered a general part number that can be compatible with thousands of types of computers. That smaller number can vary from system to system, but the the general part number will not change. Essentially, CT4951624 simply tells us that this module is compatible with your system. Regarding the voltage, the fact that it is listed as 1.35v/1.5v means that it will work with either voltage. So, if you are looking for a module compatible with 1.35v you can buy that part. Additionally, if you were looking for one that worked at 1.5v this part would still be compatible. I hope this information has been helpful. " I also read several reports about the Crucial/Amazon modules being hard to seat...needing some force to get them in. Mine slipped in without any pressure at all, a perfect and easy fit. Other reviewers also mentioned having to wait a long time for a reboot or having to reboot twice with the Crucial/Amazon RAM. My iMac booted up normally the first time. So Crucial may have changed some of the specs from what was being sold here early on. SUMMARY: Since installing this Crucial RAM my iMac has been running flawlessly. So based on my personal experience the Crucial RAM being sold here by Amazon is a perfect fit! I'll update my post should I run into anything unusual. Hope that helps anyone that follows!