cv4cfa

.9 mm mechanical pencil. I think that this sucker left enough graphite on the paper for a copying machine to pick up, which is the reason why the CFAI prefers you use pen.

Some mechanical pencils leave very very light marks on the paper - but you can definitely get ones that work. Pen really hurt me last year, and the calmness that came from being able to erase and refine an answer really helped this year IMO.