I think the no line bi or tri focals are only good for desk /reading type work---in the real work world (away from a desk and chair) they are pretty well more of a pain than help--with them you need to be looking squarely at whatever and in welding sometimes you can't turn your head/helmut and need to focus out the corners of the glass---a larger single focal lense would be best and needs to be for focal lenght that YOU weld at