Sturdy construction. Magnet holds strong at in-town speeds. Tested when no wind was present, light began to shake at 45mph and became mildly unstable at 55mph. Magnet holds up to heavy braking and sharp cornering. Only a thin adhesive sticker separates the magnet from the vehicle's paint. Marring of the paint likely if the contact points are not kept clean. 12v 50w bulb puts out plenty of light to be noticed during bright sunlight and is extremely bright at night. Worm gear that rotates the reflector is quite noisy. This light is a bit large for use on a vehicle dash. I would recommend using this light with larger trucks or SUVs.