A couple years ago I made the one for the kid's bikes. When I asked them what they wanted for a design in the middle they both immediately yelled "Ghost Rider!" That's what gave me the idea for the skulls to hold the helmets. The original plan was just to use the iron pipe by itself. Fortunately, because it was almost Halloween when we made it, I was able to score the skulls at Home Depot for $9 for a 3 pack! I don't know if HD still sells the skulls, but they definitely did in October of 2019.Where are you getting the skulls from?