I love my EVT Safe Zone helmet mirror. Rarely gets knocked out of position, nice BIG mirror, and the mount has enough flexibility for me to be able to position it to see over my shoulder. I do ride fairly upright though. They're a little pricey (circa $40) but really look built to last. I use mine nearly every day, and after more than six months it shows no signs of wear. Can't recommend it highly enough, totally worth the money. I'll never ride without a mirror again. Bar end mirror was too far away etc, and I was leery of smaller helmet mounted mirrors. The stem on the Safe Zone is pretty long too, which I think helps get it into the ideal position.