Pentair Rainbow OTO Solution No. 2 - 0.5 oz. is used in No. 782 and No. 783. This replaces Solution "A". Routine pool maintenance will help you keep your pool looking clean, sparkling, and inviting day after day. Having the right collection of pool maintenance products and accessories at your disposal helps cut pool maintenance chores down to size—leaving you more time to enjoy your pool with family and friends.