This is a set of the left and right side rubber hard drive bumpers for a 13" Macbook. Select the model that matches your system. To determine which system you have, look at the Command key located next to the spacebar on your keyboard. If your command key has the Apple logo on it, then it is one of the original Core Duo or Core 2 Duo models. If it has the word "Command" written out, then it is one of the Santa Rosa or Penryn models.