the leads in the mechanical pencils are either .05 mm or .07 mm and usually much harder because of the size of the lead...they come off so easily, that hand quilting will take it off during the quilting process. i have never marked a quilt being sent to a LA quilter and do not mark when i'm doing it, other than a few registration marks with chalk. #2s are soft and therefore mark the fabric easily...if you have had no problem getting it out then i'm glad, but i have had real problems and NEVER touch my quilts with pencils anymore... i don't wash anything with a pencil mark in it because i have had it 'set' the marks... the fabric erasers are just great and take it out fine...