They work very well once they are attached. But it was very hard (for me) to attach it to my Encore hearing aid.
The best thing about these is obviously the price. But as someone who has been wearing a pair of Phonak $6000 hearing aids for the past 8 years, I can honestly say these are a terrific alternative. I bought two thinking that even if they were just OK they would be a good backup or good for when I want to go outside and be active and could possibly get the expensive ones wet or damaged. They exceeded all my expectations. BUT... you really need to take the time to customize them to your hearing level and ear size. They give you all the tools to do this, but it will take you a few days or weeks to figure out what works for you. I am a relatively small female, and I ended up finding that the open, small ear domes worked best for me and were most comfortable (they come with the medium, closed domes attached). I saw in a lot of other reviews that people complained about the ear domes getting lost in their ears. THIS HAPPENED WITH MY $6000 HEARING AIDS AS WELL (I had to go to urgent care one time to get one removed). You really need to make sure these things are attached well and if they start to get worn or stretched to replace them. I also found that Setting 2 and mid-volume worked well on one ear but a higher volume was needed on the other ear, which was not surprising because I know that my right ear is worse than my left. One other thing: I open the battery compartment every night after I take them out to save batteries. When you close the battery compartment the next day the aids go back to the default setting, so you have to take about 30 seconds to set them to your preferred settings again. And finally, they send a return shipping label with the aids, so they are serious about their money back guarantee. I won't be returning mine; I love them!