Abstract: The invention provides an improved device for checking the concentricity of a cylindrical workpiece. The device comprises replaceable pin members detachably mounted in parallel V-shaped supporting members, the upper surfaces of the pin members forming linear contact with the workpiece under test. When the workpiece contacting surface of a pin member becomes worn the pin is either rotated or replaced by a new one to provide a virigin linear surface for contact with a workpiece. One of the V-shaped supports is slidably mounted to provide for lateral movement with respect to the other. V-shaped supoprts having different included angles can be employed to accommodate testing of centerless ground parts having multiple lobes.