The Zep Commercial Mould & Mildew Stain Remover is a ready to use, professional strength formula that quickly dissolves stains caused by mould and mildew. It uses the power of bleach to safely whitens surfaces such as fibreglass, tiles and grouting. It can be used both indoors and outdoors but works best in bathrooms and kitchens where it is most humid. It can be used on toilet bowls, sinks, baths and surfaces such as ceramics and acrylic.