Reagents are hermetically sealed in an ampule to protect from chemical instability

They are used by holding the dropper upright and squeezing it to crush the ampule inside. The dropper can then be tilted for convenient, drop-by-drop dispensing. Each ampule contains a 1-day supply of premixed reagent and has a shelf life of one to three years without refrigeration. Flat bottoms allow the droppers to stand upright on the benchtop.