To each of you who is considering purchase of a breathing exerciser, here are a few considerations:

What are you trying to accomplish? Deeper inhalation, full exhalation or both? Or clearing persistent mucus, congestion or rattles? Do you have underlying lung conditions? Asthma, COPD, Emphysema, Bronchiectasis, Pulmonary fibrosis...

Each of these situations may require a different type of device. You need to consult with your pulmonologist or other provider.

Do you get frequent colds, viruses, pneumonia, bronchitis or sinus infections?

All breathing devices need to be regularly and thoroughly cleaned because with every breath you are depositing warm, moist air as well as any germs you have in your system. Atmospheric bugs from inhaling through the device add to the mix. Mere rinsing, or even washing in dish soap is not enough to kill the most persistent of these. So you need a device which can be disinfected thoroughly at east once a week. If you have underlying conditions, or frequent infections, you may need to follow a more rigorous disinfecting routine. (By the way, this applies to inhaler housings, spacers, nebulizer cups & mouthpieces and CPAP masks - each has a recommended cleaning and disinfection routine. Or, if disposable, a number of days to use.)

Or you can elect to use no device, and go with breathing exercises. Here is just one example from the Lung Association:
https://www.lung.org/lung-health-diseases/wellness/breathing-exercises
Whatever you decide, kudos for being proactive about improving your health!
Sue