This memory I have in an Apple MacBook MB402 13.3 inch notebook white (Intel Core 2 Duo 2.1GHz, 1GB RAM, 120GB HDD, DVD + - RW DL, Mac OS X) installed. Works perfectly. However 4GB seem awful lot for being such a Macbook: after starting from about 15 programs were loud `top 'still 2GB of physical memory.