Mine was a very inexpensive model. No off-on switch, no darkness control, no batteries to change, no nothing. You do have to leave it out so the solar batteries can charge up. Leave it in a dark cabinet a month and it won't work. I leave it in a clear plastic bag to keep it clean and it works very well.
What I don't like is, when you are welding in a confined area and the light from the arc doesn't hit the tiny sensor in the corner of the lense, the lense will not darken. If the sensor is not in direct line with the arc, it will not darken.
I like the helmet very much. Just took a while to get used to it. Every time I put it on I still try to nod my head like we had to with the old helmets.
