Purity Pool OS Out Spot Stain Remover Fast and easy with no setup Small amount of acid used will not affect pool chemistry Gentle application of acid is much safer on the pool surface than other stain removal methods Fast and easy with no setup Small amount of acid used will not affect pool chemistry Gentle application of acid is much safer on the pool surface than other stain removal methods Since the pad is just for applying the acid and not for scrubbing, will last years when used correctly Handcrafted in the usa with pride