either size will work. It usually just boils down to what ya can find as it goes in spurts. there have been times I searched for 1/64th for 3 months or so and everyone was out so went to 1/32. the real thing is are your eyes good enough that you are going to see a 1/64th of an inch difference? so whichever you canget will work. Dick Blick carries it not sure on the url either dickblick.com or dblick.com

Joe