Dell XPS 15 memory upgrades

After i recieved my new machine , i was that impressed with it that some other people decided to get one too , one of them my brother in law , his spec is practicaly the same as my , the only difference is the RAM memory , his machine uses 2x2GB = 4GB RAM mine uses 2x4GB RAM . He wants to upgrade his Ram to the same as my , the problem is that we cannot find identical RAM's , not even from Dell .
The specs of my RAM - ( CPU-Z reading )
#1
Samsung DDR3 4096MB 1333MHz
PC3-10700(667MHz)
part number M471B5273CH0-CH9

every search comes up with pc3-10600 instead of 10700 what does this mean ? Where can you buy identical sticks ? Can you mix 10700 with 10600 ?It seems impossible to get the exact memory i dont understand why , if the laptop comes with certain type of RAM Dell upgrade offers different version and different part number

 

Why does he want identical as yours. There is quite a lot of brands. I just got Corsair 2x4 GB. Works great.

 

I think he want to upgrade 1stick first and then later the second one , and we think that it is not ideal to mix different types of memory .

 

Honestly RAM is RAM is RAM. As long as it POSTs and passes a few rounds of Memtest, who cares? My Alienware M17xR2 has 1 4 GB stick of Elpida RAM and another 4 GB Hyundai stick. Both haven't BSOD yet and passed a night of burn in testing with Memtest.

 

Op just tell him to buy a 8gb set. Then you'll know it matches.

 

Thanks lads , i just tell him to get the Corsair set .
But i would still like to know what is the difference between 10600and 10700 specification , just because i have never seen them before .

 

I did some more research and i have found out that 10700 =10600S , i dont know what it means but this information might be to some use for someone in the future .

 

from wikipedia:

the 10666 is the peak transfer rate in MB/s. I have read that 10666 is frequently rounded because people don't like the number 666.

 

Thank you .