DampRid Mildew Stain Remover Plus Blocker keeps surfaces cleaner Longer. 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 shield that works continuously for up to 3 months to protect surfaces and materials from odor or stains caused by moisture. And, its effectiveness is not diminished by washings or rain. Mildew Stain Remover Plus Blocker can be used indoors and out on: counters and sinks, shower curtains, tubs and toilets, doors, walls and ceilings, aluminum, glass, fiberglass, stone (except natural marble), cultured marble, acrylic PVC, vinyl, porcelain, rubber, chrome, Formica and more.