A lapping tool capable of increasing the accuracy of a lapping operation, extending the life of lapping tool itself, adjusting a lapping diameter, and coping with the lapping operation of various diameters, comprising a lapping tool body having a lapping part on the outer peripheral surface thereof and slits provided in the lapping tool body axially between the tip part and the base part thereof. Pharmaceutical compositions containing the compounds and methods for their use are also disclosed. The ionization gauge can have a plurality of electron sources andor collector electrodes.