The 2F8K3 battery is for the Alienware M17X 5th generation (R5) and M18X 3rd generation (R3) laptops. The M17 laptop has a 17" screen and the M18 has an 18" screen measured diagonally).
This battery is an internal battery which requires the case to be opened up in order to charge the battery. In order to ensure that you receive the correct battery you should take your battery out and compare it to the picture above.
Note: If you have a removable cartridge battery, this is not the correct battery. Earlier versions of this laptop use a different battery. (R1, R2 etc.).
We use the highest quality lithium-ion battery cells that charge faster, last longer and weigh less than cheaper, lower quality batteries. Each 2F8K3 battery is backed by a 2-year warranty and 30-day money back guarantee.