Simply Auto BS002 Blind Spot Mirrors, 47mm Black, Twin PackWhat is a blind spot? It sits just behind and to the side of you, in the gap between what the wing mirror shows and what you can see over your shoulder, and it is exactly big enough to hide a car. Simply Auto Blind Spot Mirrors fill that gap to enhance road visibility and in turn road safety.The glass is convex, which is what makes it work. A curved mirror covers a much wider angle than a flat one, taking in the stretch of road alongside you that the main mirror cannot reach. The two work together: the small mirror tells you something is there, the main one tells you how close. Useful for learners and newly qualified drivers, and for anyone who would rather not rely on a shoulder check alone.Where to put them: The usual position is the outer top or outer bottom corner of each wing mirror, angled outwards and slightly down. Set them with the car parked and a second vehicle alongside: adjust until the car that has just left your main mirror's view appears in the small one. Done properly there is no gap between the two.Fitting takes a minute. Clean the mirror glass with a quality glass cleaner, peel the backing, press the mirror into the corner you have chosen and set the angle. No drilling, no wiring, and nothing that stops you using the main mirror as normal.At 47mm they are small enough to sit in a corner without eating into the main mirror. Useful on any car, and more so when towing a caravan or trailer, where the blind spot gets considerably larger.