I am a basketball player who practices indoors where we are forced to wear masks. The first few weeks I played normally using those blue cotton masks that they give out everywhere, and that mask kept caving in, causing me to feel suffocated and as though I was being waterboarded. After finding out about these I instantly bought some and have not regretted it since, and playing with these on when wearing masks is a must. The way it works is that its a skeleton to your mask, so that when you breathe in, your mask does not cave in, and stays in place. This creates an air vacuum that sucks air from outside into your mouth. If there was no skeleton, the vacuum would not be created since the mask would collapse as a result. Simple physics and as an engineering college student I appreciate this new invention for these pandemic circumstances. Do buy one if you need to do exercise with masks on, they are a game changer. My 1 negative review is that these mask frames are a little small, but they work perfectly for me, but just wish there were different size options. That being said, the normal ones do work very well despite feeling a little small, but after getting used to you dont feel a thing and you dont even notice that its there.