In a dynamic pressure bearing, when a step portion is formed on the inner peripheral surface of a sleeve and radial dynamic pressure grooves are formed on the inner peripheral surface of the step portion, the width in the axial direction of the dynamic pressure grooves is set to be slightly smaller than the width in the axial direction of the step portion. In some embodiments, the invention relates to an apparatus having a centralized handle and opposing hooks extending away from and attached to opposing ends of said handle. Additionally, a tube wall thickness of the at least one measuring tube is ascertained by inserting the excitation input variable and the response variable into a transfer equation.