Made in Switzerland. Pressure between 2 and 10 bar (20 to 100 meter deep). The glass of water resistant watches is distorted by the compressed air. A barometer measures the distortion of the glass in 1/1000mm. The glass of watches which are not water resistant cannot be distorted as the air penetrates inside them. In that case the barometer shows a value of 0. Watchmakers can determine whether a watch is water resistant within one or two minutes. You will find it extremely useful for your improved customer service as it simplifies water resistance checkups after battery replacement or repairs. Air compressor is not included.
Swiss Begral Waterproof Tester by Air Pressure (HT-170)