My first binder was an Underworks binder. It was very uncomfortable underneath my armpits. My back was killing me constantly. I am very large chested, so i'm not sure if this was a factor in how uncomfortable the binder was. Last week, I bought a binder from GC2B (i found them on instagram) and the binder is so unbelievably comfortable, no pain or discomfort under my armpits, and my back hurts much less than it did while wearing the Underworks binder. I would highly recommend this binder. Also, it actually is much more effective in producing a flat chest. In my Underworks binder, in certain shirts you could see that I had a chest. With this one, you can't tell AT ALL. I also like this place because they are LGBTQ owned and they are creating these binders specifically for transitioning. They also responded to all of my emails (very quickly) regarding sizing, style, color, etc.