From the manufacturer 

This mirror is so well-received by customers that they claim it is the best helmet-mounted mirror available. Well, they also say it is the best mirror out there, period!
 

That’s what we intended when we designed it.  The HUGE 2.250” mirror which yields a huge field of view is by far much larger than anything else available.  The large mirror size makes it easy to view EVERYTHING approaching from the rear, more or less simultaneously while looking straight ahead.

The STURDY mounting is unparalleled....no weak adhesives or fragile parts used!   Additionally, the linked stalk retains it’s easy to adjust functionality FOREVER; Guaranteed never to loosen! . Simply attach to helmet with included zip-ties,  bend it into a position that offers best visibility, and it stays put!

No Blind Spot!  Since this Mirror is most functional when 5” away from eyes and up to the left, you actually look into it with both eyes, and, since you are viewing the road ahead with both eyes, the field of view ends up being unobstructed.