8GB 2 X 4GB Memory for HP ProBook 6550b DDR3 PC3-10600 SODIMM RAM (PARTS-QUICK Brand) at Amazon.com
HP ProBook 6550b 15.6" Widescreen Laptop - with Intel i5-520M 2.4GHz, 4GB RAM, 128GB SSD Hard Drive - Windows 7 Professional 64 - Used with FREE 3 Year Warranty provided by CPS. - Walmart.com