so im buying a new slave cylinder and want to know if there is any difference between these two? (Slave cylinder vs. concentric slave cylinder)

 

for our cars, no. CSC is the common reference. it takes the place of a traditional throwout release bearing. if your car is out of warranty and you are paying out of pocket you might want to look into the heavy-duty CSC units available in the aftermarket. lots of guys go that route to avoid future problems.

i'm assuming your original CSC failed on you. i recommend changing the clutch master cylinder while you are at it. they sort of go hand-in-hand and if you are keeping the car for a while it would be prudent. i just had my CSC done under warranty (nissan parts, not HD unit), but i paid extra to have the master cylinder done at the same time. then the dealer flushed/bled the hydraulic fluid with "GTR" fluid under warranty as well.