Thank you for your interest in these cannon extensions! The material used in the photo with the Sharpie coloring is black strong and flexible. Like white strong and flexible, it has somewhat of a rough surface. The Sharpie seems to stick to it very well and it hasn't been rubbing off on my fingers when I handle the pieces. I think it would look better with Testors silver model paint as the parts would then better match the silver cannon barrels on UW Bruticus.