This ceramic fiber cartridge filter was introduced in the 2004 Hot Spring high performance spa models. In 2006 the HotSpring 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. You don’t have to clean it as often either! This filter can replace the HotSpring model 71825 filter in all 1990-current Hot Spring spa models, 1998-2002 Hot Spring Hot Spot models and all Hot Spring Solana X, Hot Spring RX, Hot Spring SX & Hot Spring TX spa models.