Original Listing...
This offering is for a used Micron 8GB memory module. It's DDR4 (Double Date Rate - Type 4) SDRAM (Synchronous Dynamic Random-Access Memory) running at 2133 MT/s or MegaTransfers/second. This is not to be confused with the true clock speed of 1066 MHz x 2 (because DDR memory performs two operations per cycle). Said another way, MT/s is sometimes labeled as effective MHz, which is why we also see the clock speed of 2133 MT/s referred to as 2133 MHz. Then there is memory timing...measured as 10 for this particular memory module. This number generally describe latency, which is the amount of time between memory operations (including the amount of time it takes for memory to respond to a data request). So in summary, higher clock speed numbers are better (because this tells us how much data our memory can move...send/receive...per second), while lower timing/latency numbers are better (because this generally measures the delay between memory operations).

I also want to confirm this is a DIMM (Dual-Inline Memory Module) with 288 pins that is intended for a desktop computer. For those that are interested, you may also see this memory labeled as: "PC4-17000". This labeling indicates this module is unbuffered (or non-registered) and has a memory bandwidth of 17.0 GB/s (or 17000 MB/s). Please note the bandwidth (17000 MB/s) should not to be confused with the transfer rate (2133 MT/s). At the risk of getting too far into the "weeds", all personal (x86) computers use a 64-bit (wide) memory channel. When this channel includes DDR4 memory running at 2133 MT/s, the bandwidth of 17000 MB/s may be computed as follows: 2133 MT/s * 64-bit channel * 1 byte / 8 bits = 17000 MB/s. Lastly, the PC4 part of this labeling is similar to the DDR4 labeling above. In other words, this labeling is an indicator of Type 4 memory running at a fairly standard voltage for Type 4 DIMMs (so this memory runs at 1.35 V). 

Then there is the "2Rx8" labeling that refers to the memory rank. As I understand it, a memory rank consists of a 64-bit data bus of memory chips on a memory module. A "1R" reference indicates there is one (1) memory rank per module (so likely having memory chips on one side of a module), while a "2R" reference means there are two (2) memory ranks per module. As you might expect, "1R" memory is sometimes referred to as single-rank and "2R" memory as dual-rank (with the latter usually having memory chips on both sides of a module). In theory, dual-rank memory is generally considered better due to lower latency, because memory ranks can be accessed independently. I say in theory, because not all processor memory controllers are powerful enough to run dual-rank memory at the same frequency as single-rank memory. My research indicates that memory controllers on Intel 8th generation processors (or newer) and AMD Ryzen 3000 series processors (or newer) for personal computers are capable of maximizing the benefits of dual-rank memory. So anything older in terms of a personal (desktop) processor may not be designed to take full advantage of dual-rank memory.  Finally, there is the "x8" labeling. This refers to the bus width of the individual memory chips, and is related to the arrangement of the internal memory banks. For example, we know that each rank is a 64-bit data bus, so a "1Rx8" memory module will have 8 memory chips on it (64 bits per rank / 8 bits per chip = 8 memory chips). Generally speaking, the more memory chips on a module means more memory banks, which effectively decreases latency and increases bandwidth because accessing data in different banks is faster than accessing data in the same bank.

The history of this memory is that it was originally installed in a Dell OptiPlex computer and I acquired a number of similar 8 GB modules. As it turns out, I simply have more of these modules then I need, so I can make this one available.

Note to international customers regarding customs...
We also apologize to those that feel their country import taxes, duties and brokerage fees are excessive. As a small US business, we are required by customs' laws to declare each order as a retail sale. Additionally, the declared order value must be equal to total store purchases and/or winning auction bids (less any shipping costs, as these are not considered in the declared value). As a result, each customer will be responsible for paying his/her own country taxes, duties and brokerage fees, which will be collected upon delivery. Again, we apologize for these additional costs, but we cannot afford the penalties and fines that come with breaking customs' laws...so we have to strictly abide by them.