Hello Juanla, it is not necessary to get RAM as a kit; however we do recommend it. There are some sticks of memory that show the same speed, size, voltage and timming, but the structure is different.
Would you please provide me the complete model number of the RAM you purchased in order to double check it?
Also, could you please provide me the model number of the motherboard and processor you are using?
Hello Sylvia. Thank you very much for your response. Well i'm using a dh87mc with a haswell i5 4430 cpu. it has 2 sticks of memory (not a kit) and they are labeled as follow (both). manufacturer: kingston technology hyperx KHX1600C9D3B1/4G 4GB DDR3-1600 CL9 240-Pin DIMM Assembled in China 9905402-533.A00LF I'll hope for your answer Thank you again!