What thickness of paint roller is better for painting a flat ceiling?

Some paints stores say used a 10mm roller as it will give a better appearance on a drywall ceiling, while others recommend a 6mm roller. Which roller would be be better and why?What thickness of paint roller is better for painting a flat ceiling?
It is my understanding that if the surface is flat, you need less nap on the roller. The large fluffy ones are more for textured surfaces, such as stucco.What thickness of paint roller is better for painting a flat ceiling?
I'd use the 6 mm. This assumes a smooth or nearly smooth ceiling. You'll get less issues with the roller sliding instead of rolling and less dripping.





The deeper pile rollers are for textures, not for holding more paint (even though they do hold more paint) The thicker pile being squeeezed against the surface to be painted, when its smooth, wiill squeeze out a LOT of paint and make a huge mess.
1/4 for new construction 3/8 for older homes allways worked for me 3/8 just covers better for all applacations i think just not when dealing with stucko
use the 10mm to cover drywall it does give it a better look and coverage.
1/2 inch