I have bought these cells on 3 separate occasions. I've built two 48v packs with 16 cells each and one 36v pack with 12 cells. I've tested each cell individually for capacity and internal resistance and every cell is very close in tolerance. These are not chinese knock offs these are very high performing cells capable of 10 amp charging and 60 amp discharge from a single 4500mah cell if not much higher. At a constant 6 amp charge immediately followed by 6 amp discharge they are not warmed above room temperature where the lesser brands would be on fire. These are the real deal. They come as individual cells you can build into a battery pack. If you are putting them in series you should consider a Battery Management System (BMS) made for LiFePo4 batteries. Cost is $17-$50 depending on where you look.