The laptops use PC100 SDRAM SO-DIMMs. Sony PCG F Series laptops use non-registered, unbuffered, non-ECC RAM. All replacement and expansion RAM comes with a 30 day money-back guarantee. The SO-DIMM chips are half the size of regular DIMMs and are specially designed to be used in laptop applications. For compatibility questions or assistance choosing the right memory for your needs, call us at 1-888-861-0328.