Fowler's Bore Gage Setting Master Kit is used for accurately setting any bore gage up to 6" /150mm in diameter to an accuracy of 0.0001" /0.003mm Each Set includes:Setting DeviceBase anvil: 2.750" x .80" Adjustable anvil 2.375" x .375" (two each)Internal capacity: 6" /150mm Depth capacity: 1" /25mm Centralizer capacity width: 2.625" /66.7mm Quick-release holder for fast adjustment.Can also be used of external setting, depending on application (external mice, snap gages, caliper gages)Economy Gage Block SetsMetric model:33 pieceAS-2 gradeCertificate of Calibration to N.I.S.T.