Then I found two sizes of balls (3/16" and 1/4") that were available with either holes or tapped holes in these hobby packs. The manufacturer calls them "nibrass", which seems to indicate that they are nickel-plated brass. It got even better when I found that you could order just the balls in bulk. Last time I ordered, the 100 piece bulk packs were in the $60 range. 60 cents for a ball that is already tapped seems like a very nice deal to me. Check the "Parts Sources" part of this site for more information about getting these balls.