Full Details from Amazon.com : http://www.amazon.com/gp/product/B00OM8YMIC?tag=onigi-20
4GB PC3-12800 (1600MHz) DDR3 DIMM Upgrade for Dell Inspiron 660s
4GB DDR3L SDRAM - DIMM 240-pin
Non-ECC unbuffered
1600 MHz PC3-12800
100 Compatible with All Major Brands
Limited Lifetime Warranty