Masquerade Tattoo, Inc. | Glossary of Terms

Tattoo Needles;

Definition: A tattoo needle is actually (usually) a group of several small needles called sharps attached to a needle bar.

Also Known As: group, single, liner, round, flat, magnum, shader

Examples: Needles can be made in groups of 3, 5, 7 or more, depending on what the artist is comfortable with and what the design calls for. Occasionally, a single needle can be used for fine lining, but this is not very common. The sharps are soldered to a needle bar, and the bar is placed in the tattoo machine through a tube. Needle groups also come in different shapes such as round (for lining) and flat (for shading).

about.com has a little info on tattoo needles.