The replacement filter cartridge for the RM257ACRS refrigerator is part number DA29-00012A. Please click on the following link for information and availability: http://www.samsungparts.com/Product...
Please confirm your refrigerator model number, since the DA29-00003B is compatible with a number of current refrigerator models. Models that use the DA29-00003B can also use the DA29-00003G. If you type your refrigerator's model number into the appropriate search field on SamsungParts.com, it will tell you which filter is compatible.