Original OEM coreless Bullfrog Spa Replacement filter for A series, R series, and X series for late 2017 models with standpipe. This Bullfrog replacement filter is specially designed for 2017 and newer Bullfrog Spas that have the plastic standpipe and cap in the filter housing. This filter does not have threads on the bottom!

2013 - 2017 spa models require threaded bottom.