Prevent rust stains in your appliances and fixtures with Compass Minerals(R) Suresoft(R) Pellets Plus with Rust Buster(R), a highly soluble 99.8% pure formula that softens water, reduces rust build-up, and fights odor. The salt cubes are sized to scour and dissolve easily in your water softening system. | Sure Soft Pellets Plus with Rust Buster | Size 40 lb