I bought mine for $65 from Harbor Freight about 6 years ago and it works fine. It's solar powered so requires no batteries. The one we have at school requires a 9-volt battery and has to be turned "ON" to work. When it's "OFF" or the battery is dead, it is quite dark normally, is difficult to see through, and does not work correctly. Both of them, when working properly, are about like wearing dark green sunglasses when not welding and go very dark instantly when you strike an arc. Check to see if the one you have requires batteries...