SPI Micrometer Anvil Set Features include... 7 slip-on pieces Held on with own reinforced neoprene boots. Measure hard to reach places and odd workpieces. (Shoulders, webs, slots, grooves, etc.). All anvil attachments other than ball, subtract 0.500" from total reading. Subtract 0.175" for ball. Furnished in a plastic case Anvils include... Spline Anvil: 0.100" Knife Anvil: 30° Angle Super Spline Anvil: 0.050" Face Blade Anvil: 0.300" Thick Comparator Anvil: 30° Point Disk Anvil: 0.500" Face Ball Attachment Anvil: 0.200" Diameter