Caliper Accessory Centerline Gage For use with 4" & 6" Calipers with 0.142" Jaw Thickness or less Pair of conical probes specially designed for calipers to quickly measure centerline distances. The 60° conical probe snugly fits into holes and takes away guesswork from center distance measurements. Features include... Diameter "A": 0.375" Overall Length "B": 2.187" Slotted Width "C": 0.141"