This "mineral sanitizer" introduces silver ions into the spa water, inhibiting bacterial growth. It is designed to suspend inside of the filter standpipe on all 1990 to current Hot Spring, 1992-current Tiger River, all Limelight models, 1998 forward Hot Spot and all Solana spa models. This continuous silver ionizer cartridge will charge the water one time and that "charged" water will last for four months. Two year shelf life when kept in a dry place.