This Star Brite Mildew Stain Remover quickly removes unsightly mildew stains from fibreglass, vinyl, plastic or painted surfaces. It begins working on contact. The special buffered-bleach formula will not harm vinyl upholstery or threads. It is a much better alternative to using regular laundry "bleach-water" solutions and can also be used around the home or in RVs wherever mildew stains are a problem.