I have a collection of about 6 or 7 of these that I made, all about the size of a baseball did you start with rubber bands or did you cheat and use a ball of some sort? Oh I see you started with a marble I start with a rubber band which I knot a bunch of times until it's possible to wrap rubber bands around it. It's a challenging method but I feel like I do a better job when It's done like that.