Sure, you could also use a wooden bead or part of a golf tee. I used a .25 inch ball because that's what I had. I also made a couple using some wooden beads I found. Size or material isn't important so long as it's big enough to not go through the holes, small enough to fit inside of and smooth enough not to cut the tubes.Looks good, Henry, but couldn't you enlarge the countersink in the front of each fork and use a 3/8" ball? You wouldn't have to tie the ball in that way. Nothing wrong with how you're doing it, I'm just curious.