LC3 Liner Cleaner & Stain Remover is a natural, biodegradable, non-toxic cleaner that is safe to use on vinyl liners, fiberglass walls and acrylic spa surfaces. Though it cleans with the power of acid, it is as gentle as dish soap! The non-corrosive, non-fuming, viscous formula clings to surfaces for longer, deeper penetrated cleaning. Simple, safe and effective.