The Flute Depth Tester is a precision instrument specifically designed for measuring the flute depth of corrugated paper, filter paper, and various fluted materials. It also supports thickness and density calculation. The device fully complies with standards including ISO 534, GB/T 451.3, GB/T 1983, and QB/T 4031-2010. It features a specialized V-shaped anvil and a narrow, elongated measuring head (length 16±5 mm, width 5 mm, V-angle 60°) that can accurately reach the bottom of flute valleys, ensuring reliable flute height data. The measuring range is 0-18 mm with a measurement precision of 0.001 mm, measuring pressure ≤2 N, and parallelism between measuring surfaces <0.035 mm. The ultra-low measuring pressure design effectively protects flute structures from deformation during measurement. With overall dimensions of 80×120×120 mm and a purely mechanical structure, it offers simple operation without electronic drift, making it an ideal specialized instrument for flute depth inspection and quality control in papermaking, filtration materials, and packaging industries.