Horizon EXACTA 3 levels, ACCURACY 0.3MM/M = 0.017° (IN THE BASE POSITION), reinforced ALU profile 2.2mm, milled base, liquid in the levels UV stabilized and fluorescent, otic horizontal level - easy and more accurate measurement, double rings in spirit levels allow you to set a slope of 2%, the spirit level is resistant to operational shocks, EACH PIECE ELECTRONICLY TESTED.