Home Armor® Mildew Stain Remover Plus Blocker is no ordinary cleaner. It's safe, powerful bleach-free formula eliminates mold and mildew stains, soap scum and mineral deposits like calcium and lime. But, that's only the beginning. As it cleans, it leaves behind an invisible mold and mildew resistant finish that works continuously for up to 3 months. And, its effectiveness is not diminished by washings or rain.