Happy Hot Tub 3 x Tri-X Filters Hotspring Hot Spring PWK30 Replacement Cartridge Part Number: 73178 (3 pack) This Spa Filter is designed to fit the following hot tubs and spas: Grandee 1991-Current, Vista 2004-2013, Envoy 2004-Current, Vanguard 2001-Current, Grandee NXT 2014-Current, Envoy NXT 2014-Current, Jetsetter NXT 2014-Current, Jetsetter 1991-Current, Prodigy 1991-Current, Sovereign 1991-Current, Alccolade 2005-2006, Landmark 1997-2003, Aria 2007-2015 and Highlife ILE 2003. This ceramic fiber cartridge filter was introduced in the 2004 Hot Spring high performance spa models. In 2006 the Tri-X became available as a replacement for the common polyester filters (aka paper filters). The unique design enables it to filter twice the water per minute than a common filter. No matter the model of your spa or hot tub, or when it was made - it's important that you regularly change your filter to prevent bacteria build-up. Choose from our selection of hot tub filters to find the right replacement hot tub filter for your spa - at the right price! Hot Spring Spa filters are a vital part of any spa system. Spa filters regulate the water that enters your spa and keep debris, dirt, and other items from floating into the pipes and damaging the pump and inner workings of your hot tub.