FEATURES Easily applied by snapping on to end of either anvil or spindle, thus permitting two attachments to be used together Balls are hardened, measure .200" in diameter, and move freely in the retainer, insuring positive contact with anvil and spindle SPECIFICATIONS Made in America: Yes : Diameter: .200" (5mm) Fits Starrett Series: For 224B through J, 238, 239, 436 Micrometers and 663 Micrometer Heads, .300" diameter Anvil and Spindle