Have the unit get recommended by my breath therapist, informed me about it on the net and was then convinced because it is used for example in many lung specialist clinics. Since it is constantly with me and my family in action - for our needs, however, almost exclusively with the coarse-studded disc, which we ordered it. A good description of equipment and applications is, but worth it for intended for use in continuous use the advice of professionals obtain (technical and sports doctors, therapists ... etc.). Very professional equipment, long-term fit. Everything else in the market is "nice to have" it.
