American Hydro Systems RR2 Rid O' Rust Extreme Water 2X Concentration Stain Preventer, 2.5-Gallon Bottle New 2X formula is twice as strong as original Rid O' Rust formulas Prevents ugly rust stains and scaling from well water Use in place of Rid O' Rust Formula 1000 and Formula 3000 No.1 Selling rust preventer in the US Ready to use formula