The curved surface sensor of Mitech portable surface roughness tester MR200, with totally length of 78mm, main body length of 46mm, guide-head bearer length of 20mm, main body diameter of Φ10mm, core-insert sleeve diameter of Φ7mm, guide-head height of 7.8mm, It is the optional configuration of the surface roughness tester, mainly used for measuring the surface roughness for the smooth cylinder with radius larger than 3mm. For the smooth cylinder or other curved surface with larger radius, it also can get the ideal approximately value, the larger of the curvature radius, the smoother of the surface, the better the measurement.