Fowler's Bore Gage Setting Master Kit without Gage Blocks is used for accurately setting any bore gage up to 6"/150mm in diameter to an accuracy of 0.0001"/0.003mm. Base anvil: 2.750" x 0.80". Adjustable anvil 2.375" x 0.375" (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 mics, snap gages, caliper gages).