Review on 2PCS Bike Rear View Mirrors - Adjustable, Rotatable Handlebar with Wide Angle Convex Mirror for Mountain, Off-Road, and Fixed Gear Bikes by Kevin Hauck

These very cheap mirrors are cheap plastic not glass you have to understand - concave to the point where I can't see oncoming cars anymore could see me until they are literally next to me. It can be useful to have a smaller field of view to the rear, but with a more realistic 1x image of what's happening directly behind you. As others have pointed out, the rubber straps that attach the mirrors to the bike are obviously a weak point - they are very fragile!