Great Barrier Softub® Filter – Snap-On (2009+) with MicrobanHigh temperatures and the wet environment make the filter surface a target for bacteria. Great Barrier filters are made with antimicrobial protection which inhibits the growth bacteria which can cause odors, stains, and degradation of the filter surface. If your tub was manufactured in 2009 or later, purchase the 8553 filter. Call for pre 2009 filter (#8555)