16GB KIT 2 x 8GB HP-Compaq Pro Desktop Series 3505 Microtower 4300 Small Form Factor 6200 Microtower 6200 Small Form Factor DIMM DDR3 NON-ECC PC3-10600 1333MHz RAM Memory Genuine A-Tech Brand 16GB KIT (2 x 8GB) DIMM DDR3 NON-ECC PC3-10600 1333MHz RAM Memory Genuine A-Tech Memory Lifetime Warranty Toll Free Technical Support 1-866-557-4527 Designed For HP-Compaq Pro Desktop Series. (See Compatibility List Below)