Kingston Technology 4GB 1333MHz DDR3 SODIMM RAM for Apple MacBook Pro Air - Single Rank Laptop Memory Upgrade (KTA-MB1333S/4G) - Improve Performance for Gaming, Video Editing & Multitasking

Just got this memory for my iMac 21,5 Mid 2011... I bought 4 of these to take my computer to 16GB... I didn't want to mix this memory with the original memory... wanted all modules of the same brand, size, etc. The result is that it worked perfectly... System is running for over a week and no crashes... my OS Yosemite performance has increased considerably and I'm loving it. I think my review is important because it's the first and I hadn't seen any when I purchased this product. It seems this memory is not so popular yet as the KTA-MB1333/4G.... This product is KTA-MB1333S/4G... The "S" stands for single rank... a more modern way of working with data packs. I was afraid about it, but it was totally compatible just as Kingston had said in their website and technical e-mail I got answered. This product was ideal for my iMac model. Be aware to check if it's compatible with your Mac model before purchase.