Apple 661-5861 SDRAM, 4 GB, DDR3 1333, SO-DIMM - 13inch MacBook Pro Early Late 2011 - A1278. 661-5861 for A1278 i5 2.3GHz Early 2011, A1278 i7 2.7GHz Early 2011, A1278 i5 2.4GHz Late 2011, A1278 i7 2.8GHz Late 2011. Apple Memory for MacBook Pro (13-inch Early 2011), MacBook Pro (13-inch Late 2011).
