Contact is bad. Is not it because there is painting to the threaded part? Because I use it with a feeling, I feel stress. I am sorry to think that it is very disappointing for the price and it is very convenient if you feel good.
The ultraviolet light intensity is weak, and there is a feeling that I can not rely on a bit. Because it is a cheap one among ultraviolet lights, consider that it is suitable for a price if you think that it is the minimum usable level.
I bought it for curing 100 UV resin. It will cure properly. I do not know how long the hobby will last so I made it a flashlight type so that it is easy to use for curing paint at work. Since it looks exactly like the ordinary flashlight you have, you have to be careful (haha) It seems that it's okay because the seal of "prohibiting direct ultraviolet radiation" is tightly stretched. So far for hobbies & work, there is nothing wrong.
I am a car shop. We will repair scratches and cracks by stepping stone etc of windshield. Pour resin into scratches and cracks, cure it by applying ultraviolet rays, but it was easy to carry and was looking for things that can be used with dry batteries. Although I bought it in one or eight, it cures so quickly that it does not compare with the fluorescent tube type I used before. Moreover, it is small and lightweight, it is convenient to carry and great help. I should have noticed this earlier.