Great product and excellent repair guide
My MBP had been acting strange for a while until it one day just displayed a blinking folder with a question mark on boot. Initially i thought my hard drive was broken, but replacing it didn't solve my problem. After some online searches and trying different things, I realized it had to be the hard drive cable. Found the parts and tools I needed on ifixit and gave it a shot.
The repair guide is excellent! Clear pics and easy to follow. The new hard drive cable was high quality and fitted perfectly. However, I found it a bit difficult to fold and fit the cable to get the two 3mm screws back in (see step 10). I guess I was just careful because I didn't want to break it, and was unsure of how much it could handle. Used the spudger to "tuck" it carefully in place so I could get the screws in, made it eventually and got everything back together. OS X El Capitan fresh install on a brand new SSD and everything is working great! My old HDD still works perfectly as an external backup drive, proving it was the cable all along.
Don't be afraid to bend/fold the cable, but be careful.