Actually there is a better solution out now if you want a helmet mirror which I would highly recommend as its more stable and has a wider field of view.

If you have even seen or heard of the mirrors Chuck Harris made before he passed away a company(Monkey Mirrors) now produces a much improved version that is much cheaper than the one linked on amazon and more adaptive plus they do custom artwork allowing for a little bit of custom flare. The mirror is automotive quality in both clarity and build. Ive found that with the mirror the field of view is large enough that a 5 degree head movement means I can see behind me and a 10 degree allows me to look in the other lane.



I am also testing a bar mirror as well that they will be releasing soon that permits you to have a proper glass mirror the size of a mirrycle mirror but it clamps to any bar even over bar tape meaning you can use the same mirror on both your road bike and mountain bike in the same day without having to cut the grips.