Bullfrog Spa Replacement filter for A series, R series, and X series models years 2013 – 2017. This Bullfrog replacement filter will work with 2017 models if the core is removed and filter is threaded directly into filter housing. For Bullfrog Spas year models ranging from 2003-2012, the shorter thread version is required (10-2785). Please feel free to call us at (972) 317-1011 if you have any questions about the replacement filters on your Bullfrog Spa!