8GB DDR3 Memory Upgrade for HP Compaq ProBook 4540s PC3-12800S 204 pin 1600MHz SODIMM Laptop RAM (PARTS-QUICK BRAND) 8GB PC3-12800S DDR3 1600MHz 204 pin SODIMM for HP Compaq ProBook 4540s Capacity: 8GB Speed: PC3-12800 DDR3 1600MHz Form Factor: 204 pin SODIMM Halogen Free; ROHS Warranty: Lifetime