I bought the B&M CycleStar Mirror directly from Cruzbike. To be honest, I was surprised how small it was, and almost returned it without giving it a try. It is considerably smaller than the mirror I use on my other bike, and is also smaller than a different mirror I purchased from Amazon. But the mirror I bought from Amazon, while over 3.2" in diameter and very affordable ($15), also has a convex lens, which made it very difficult for me to judge distances of the cars behind me. The B&M CycleStar mirror from Cruzbike has worked out great for me in the end, despite its smaller size. I do wish Cruzbike would update their description to indicate the actual size so it isn't a surprise to the buyer, but really it works very well. I put it on the left size of my bike, and I put the other larger mirror on the right side. I don't usually need right side visibility, but occasionally it comes in handy if I am riding with someone else behind me and they are moved over enough that they are out of my field of vision from the other mirror.