I'd suggest getting one with more than one 'sensor'. Mine only has a sensor above the glass, and once in a while, if I'm under a car or something, that little sensor doesn't pick up the welding, and doesn't darken the mask. I know some higher end models have 4 sensors picking up the welding, and darkening the unit. And, if you own a welder, and own a jeep, chances are very strong you will be welding underneath the jeep someday.