Basically there are “liners” and “shaders”. Liner tattoo needles are grouped together in various quantities in a round configuration, and are often tightened at the taper so that the points are very close together. Shader needles can also be configured in round patterns, as well as fanned out into what we call Magnums or “Mags”. There are other minor variations and some less common configurations that some tattooers use, but essentially this covers what is commonly used.
The individual needles are grouped together and soldered in place to form what is referred to as the “tattoo needle”, the needle is then soldered onto what is called a “needle bar”, which is just a length of stainless steel wire with a loop on the end which can be fitted to the part of the tattoo machine that creates the up and down motion. The unit as a whole is then cleaned, sterilized, and ready to use.
The needle bar is placed within the “tube”, a stainless steel (re-useable) or rubber and plastic (disposable) device which provides a hand grip for the machine, that allows the mechanism to function within and through it, and also to provide a reservoir for the pigment. The amount that the needles actually penetrate the skin is about the thickness of a nickel. Any given tattoo artist may work with a range of different needle groupings in order to create their own style of tattooing, it is truly a tiny stainless steel paint brush, and what sort an artist chooses is a matter of preference.