#12 gauges are highly popular across all needle groupings and tattoo styles. Anyone referring to #12 or 0.35mm needles may also call them Standards. Common in lining and traditional work as they have a faster ink flow. Great for bold lines and colour packing/shading large areas.
Keeping this in view, what are round liner tattoo needles used for?
RL or round liner needles are used for lining. RS or round shader are used for shading. Flats are used for areas with geometric shapes and shading. Weaved magnums are used for shading, blending and coloring large areas.