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In the description of firearms, the words bore, caliber, or gauge are distinctly used to indicate either the interior diameter of the barrel or the diameter of the bullet required in each case. This is variously expressed either in millimeters or in fractions of an inch.
In the case of the needles used in surgery (I do not refer to suture needles, but to those usually attached to a syringe or cannula that serve to inject or aspirate a fluid, be it liquid or gas.), the problem arises when one wants to know the exact meaning of the number stamped on a given needle. We all know that the number 30 designates a very fine needle; 25, a medium-sized needle; and 20, a considerably thicker one. But, what is the precise meaning of 30, 25, and 20? To what standard or criterion do they respond?
My efforts to find the
Urrets-Zavalía A. The Caliber of the Needles Used for Injection or Aspiration in Surgical Work. Arch Ophthalmol. 1996;114(10):1299. doi:10.1001/archopht.1996.01100140499041