The coarse-grain ultrasonic thickness probe N02, suitable for all line ultrasonic thickness gauges, it is the optional configuration. The coarse-grain ultrasonic thickness probe N02 with frequency of 2.5MHz, crystal size of 14mm, suitable for the measurement of cast iron and other coarse-grain materials, its measuring range for common ultrasonic thickness gauge is 3-300mm in steel while its measuring range for multi-mode ultrasonic thickness gauge is 3-600mm in steel. The cable length of the N02 probe is 90cm and its limitation for the minimum pipe diameter isΦ20mm. N02 probe, elaborately developed with material of piezoelectric ceramic, engineering plastic and stainless steel, integrated die casting process and splinting probe design for convenient plugging, it can effectively reduce the fault caused by frequent plugging, accurate and durable. It is widely used for monitoring the corrosion thinning degree for various pipelines and pressure vessel of the manufacturing devices in petroleum, chemical, metallurgy, shipbuilding, aviation, aerospace and other fields. It also can be used to make accurate measurement for various plants and mechanic parts.