8GB (4GBx2) Team High Performance Memory RAM Upgrade For HP - Compaq ProBook 4311s 5220m 6550b 6555b Laptop. The Memory Kit comes with Life Time Warranty. at Amazon.com
HP-6555B Pro Book
2GB Memory for HP ProBook 6555b DDR3 PC3-10600 SODIMM RAM (PARTS-QUICK Brand) at Amazon.com
Specs HP ProBook 6555b P340 Notebook 39.6 cm (15.6") AMD Athlon II 4 GB DDR3-SDRAM 250 GB HDD Windows 7 Professional Black Notebooks (VM614AV)