... measures the thickness of the poured concrete slab of non-metal like structure,concrete,wall,girder,bar,pole,wood and ... 80mmExtension Bar:φ25×600(mm)(3 piece)Work PrincipleDJLC-A concrete thickness gauge is composed of signal transmit, connector, ... precision,digital clue to aim electrodeDisplay thickness directly display without analysis also can be stored or printedSpherical direction conniction ...