I have a MacBook Pro mc700 (early 2011), and I've bought a pair of 4Gb Crucial RAM sticks. The problem is that I'm not sure whether these RAM sticks are original or not, and I'm really worried about not being compatible with my MacBook Pro. Can anybody please help me to find out whether is it original or not?
If they physically fit and pass the Apple Hardware Test, they are 100% compatible. Whether they are legit Crucial products is mainly determined by where you purchased them. If you got them online from Amazon or something, they're most likely legit.
The MacBook Pro (MC700) early 2011 supports 1333 MHz PC3-10600 DDR3 SDRAMs. Check the sticker on the RAM-module or on the packaging if it fits. Here is a link to all compatible modules with product numbers.
If they fit formally and physically put them in and run the Apple Hardware Test/extended memory test.