Take A Look Cycling Mirror with Helmet Adapter & Carry Case – Low-Tech Rearview Mirror for Bikes – fits Helmet & Sunglasses – Shatter-Resistant Polycarbonate Lens, Always On (Left-Side)

Bought the set that included the “original” mirror, interior helmet mount and travel case. Due to the design of my bike helmet had some difficulty with the interior helmet mounting option, couldn’t extend the mirror out far enough for it to be useful, also had similar issue when attaching it to my prescription glasses frame. Found the perfect mounting solution for my helmet by attaching it to the helmet visor which was suggested as an option on the company website (photo is included with this review). With its adjustable design was able to give the mirror a snug fit and it is at the perfect length to be useful. After getting it attached I found that I like using it. Its simple and unobtrusive design works well, and once attached it’s still very adjustable. The mirror itself is small but works effectively enough to give you an idea of what’s going on behind you and still allows you to keep your eyes on the road. After trying several different bike mirror options (including handlebar mounted) this is the one I’m going to keep.

It works pretty well. The up side is that it's small and discreet but the down side is it's small making the FOV limited. Also I like using my right eye (yes I realize that's opposite of the side of traffic) and this is only designed for the left eye but mostly the small size makes it somewhat difficult to focus without having double vision. I also purchased a other mirror that has a larger triangular mirror and an assortment of mounting option accessories which I like much better

I've been cycling for years and finally decided to purchase a helmet mount mirror for added safety (and to avoid those speeding power bikes). I was a little skeptical that this tiny mirror would be useful, but it is just the perfect size. It doesn't block your field of vision but is sufficient for a glance behind when changing lanes or monitoring for those power bikes. Set-up is fairly straightforward, and if you take some of the tips for adjusting, you can quickly find your sweet spot and forget about turning your head and looking over your shoulder. There is an adjustment period as you would expect, but after one or two rides, it becomes second nature. I purchased the helmet mount, but found that the glasses mount works perfectly fine.

Does work well; very snug fit; easily adjustable; placed on helmet; very light

What amounts to be basically a small piece of plastic mirror attached to a bent paperclip, it is no surprise it just does not last. It mounts to eyeglasses with some fiddling. But it rarely stays in place and the view you get from it takes a lot of getting used to. Additionally, call me weird but having this wire attached to my glasses makes me think that it could easily penetrate your eyeball in a crash. I'm going back to using the plastic mounted helmet mirror. Also, the little blue plastic helmet mount that is included simply doesn't work with MIPS helmets at all.