All TWEE products are handmade. Our artisans take great care in crafting each and every piece - from making all the way to mailing. And because of that, you might notice small irregularities - and we think that makes it beautiful! TWEE's chalk is meant to be used on surfaces with grit. This includes sidewalks, asphalt, concrete, slate, etc. TWEE chalk is more dense than chalk used on chalkboards, making it stronger and less likely to break in use and in transit.