I purchased our first lung exerciser after my husband came home from ICU with the dreaded Covid pneumonitis. He had an incentive spirometer but it only worked his inhale. After a week, we quickly understood that this lung exerciser was FAR superior! In fact, he had his 12 week follow up since he came home, and the pulmonologist said my husband has had probably the best recovery he has seen. He's still at 70% lung capacity, but is covering 5.2 miles on mountain trails in 1:21, at 15:33 minute/mile pace. He's 61 years old and was near death 12 weeks ago. I see the writing on the wall, so I just purchased my own so he doesn't kick my 10 year younger a$$ on the trails. Amazing product!