49Y3746 . Is a DDR3 Module. DDR3 Modules run from 1066 to 1600 MT/s (million transfers per second).Has a total capacity of 4GB (Gigabytes).Has a Memory Bus Type of PC-10600.Uses ECC (Error Correcting Code), ideal when system failure must be avoided at all costs. Is also registered which makes it stable enough for server conditions.You can expect the data to transfer at a rate of 1333 Mhz