Replacement Apple 661-0055 by Amstron is designed for use with the Apple PowerBook 520 and PowerBook 540 series. The LMA-12 is precision-engineered and rigorously tested to be 100% compatible with your Apple notebook; and is designed to replace battery part numbers 661-0055, M1906, M1908, M1908LL/A, and M1908LLA. Take your work on the road with you without sacrificing performance and productivity with Amstron brand Apple batteries.