Tuberculin Syringes are small syringes with fine needles that hold up to one half to one cubic centimeter of fluid, used to administer medication (antigen) under the skin and perform a tuberculosis test called PPD. Different models of Tuberculin Needles may come permanently attached to the syringe or they may be separate and require assembly. The width of the needle is known as the needle gauge. The higher the number of the needle gauge, the thinner the needle. These syringes are marked in increments of 0.01 cc. And the needles are often 26 to 27 gauge in diameter and 1/2 to 5/8 inch in length.