Tir-X Filter 65sq ft HotSpring Spa: The unique Tri-X filter is three-dimensional. Traditional filters rely upon the paper media to catch particulates in a single pass. The Tri-X filter not only filters by using the element's surface area, but it also filter's by using the media's depth (third dimension). · More Filtration Area. Because it filters by depth rather than just surface filtration, Tri-X filters ten times more gallons per square foot than other filters and it provides over twice (65 sq. ft.) the filtration area of a standard (30 sq. ft.) filter.