Choice Flasks are items used to revert an Ability specialization back to its original form (e.g., reverting Cleanse to Heal). They are especially useful for testing different specializations and finding the best fit for your playstyle.
Each ability has its own specific flask. For instance, a Healing Flask cannot be used to revert Blizzard Arrow, which is a specialization of Storm Arrow. Below is a list of the available Choice Flasks and what they revert: