The key is how you attach it to the helmet.
This is a great attachment for the Take A Look Mirror, which is the best bike mirror on the market. I am a heavy-duty rider (commute and many, many weekend miles) and would never ride without my mirror. The key, though, is how you attach it to your helmet. Forget gluing this thing to the outside of your helmet with those little sticky pads, I completely agree with the one-star review as to that method - it is not great. What you need to do is cut a small slit at the bottom of the hard-foam padding on the inside of the helmet shell to tightly fit the top tabs, and slip the top tabs up into the slit. Figure out the optimal placement of the mirror, and make the cut. A boxcutter or very small Dremel bit would work. (Remember, you can always make the cut bigger if needed, but once done, you can't make it smaller, so be judicious.) This is great way to attach this mirror - FAR better than attaching to your glasses, the angle is better, the mirror is completely stable, and, additionally, on those long steep climbs you can pull off your fogged glasses and continue to use your mirror. I have had my mirror mounted this way for years, with nary a problem, it does not come out (and, trust me, on these pothole Sonoma back roads, if that was an issue, I would have discovered it). In fact, the only issue I have had is that I have used it so long, the plastic is becoming a bit weak from wear, and thus I am replacing this little plastic piece (my mirror is still going strong).
Thank you for your feedback.