Question What is the diffrence between these two ram and which can work on my laptop?

[Peanut132]

My laptop: lenovo y520 - 15ikbn

First ram
RAM Crucial 8GB DDR4 2400 MT/s DR x8 - 260-Pin Laptop

Second Ram
Crucial 8GB RAM DDR4 Laptop SODIMM 2400MHz 260Pin 1.2V - CT8G4SFD824A

Which is compatible or both compatible?

 

[Zizo007]

What's the model number of the 1st ram?
You already have an 8gb 2400mhz stick?

 

[Third-Eye]

My laptop: lenovo y520 - 15ikbn

First ram
RAM Crucial 8GB DDR4 2400 MT/s DR x8 - 260-Pin Laptop

Second Ram
Crucial 8GB RAM DDR4 Laptop SODIMM 2400MHz 260Pin 1.2V - CT8G4SFD824A

Which is compatible or both compatible?

Both appear to be dual rank and while the cas latency is likely different on both, the rest of the basic specs should be compatible. If the cas latency is different, the laptop will default to the looser timings, but I doubt you will notice any difference other than more memory. Crucial is usually one of the better brands for mixing kits.

Edit - Find the part number of the original module through CPU-Z on the SPD tab. https://www.cpuid.com/softwares/cpu-z.html