These caps change from white to blue when your beer gets cold. Color starts changing at 46.4 degrees and at 41 degrees they are at their maximum blue tonality indication.
These 26mm Oxygen Absorbing caps have a special liner that absorb oxygen in the bottle head space.
This helps reduce the oxidation that happens during the bottling process, keeps your home brewed beer tasting fresher, and can extend the shelf life.
These caps work with standard pry off glass beer bottles, any size.