Jack's Magic The Vinyl Liner Blue Stuff is an easy, effective way to keep your vinyl-lined pool free of nasty metal staining and scale buildup. Its unique formula is designed specifically to work safely with vinyl liners, even those equipped with heaters, finally giving vinyl pool owners a full strength chemical to combat stain and scale buildup. Best of all, Vinyl Liner Blue Stuff is made by Jack's Magic, and industry innovator in pool chemicals, allowing you to buy with confidence.