Tattoo needles are differentiated by their diameters. This is indicated by the 1st 2 numbers on the needles packaging, for example, 1203RL, otherwise known as #12, 3 Round Liner. The leading number refers to the diameter of the needle so a 1203L or #12, 3 Round Liner means it has a #12, or .35mm diameter and a formation of 3 needles, arranged in a tight liner formation. #12 is one of the largest diameters available, it is also one of the most commonly used sizes. By comparison, a 1003RL (#10, 3 Round Liner) is 0.30mm. A 0803RL (#8, 3 Round Liner) is 0.25mm, 0603RL (#6, 3 Round Liner) is 0.20mm and on the other end of the spectrum is the large 1303RL (#13, 3 Round Liner) which is 0.40mm.
Diameter affects ink flow where the narrower the diameter, the finer and more controlled the stream of ink that flows out of it. That’s why #10 tattoo needles are so popular for line work; the ink flow is finer and more controlled than with a #12 or #13, but not quite as constricted as with a #8 or #6 tattoo needle.
Most Common Needle Diameter’s and their characteristics
#13 = 0.40mm in diameter and have the fastest ink flow which is good for filling in large areas.
#12 = 0.35mm diameter and are the most popular diameter size tattoo needle overall.
#10 = 0.30mm diameter and are the most popular diameter size for lining work.
#8 = 0.25mm in diameter and will have a finer, more controlled ink flow.
#6 = 0.20mm diameter and offers the most control and finest ink flow.