Arch Memory 4 GB (1 x 4 GB) 204-Pin DDR3 So-dimm for ASUS K52F-SX139X RAM Arch Memory is a Registered Trademark of Arch Computer, LLC 204-Pin DDR3 SODIMM Compatible with systems that use PC3-8500 204-Pin DDR3 SODIMM modules 4GB RAM Memory for ASUS K52F-SX139X Notebook by Arch Memory Lifetime Replacement Warranty