These threaded into my 14g Anatometal Black Niobium Circular Barbell, but not flawlessy. Took a little effort to get the ends flush with the barbell, but in the end, the onyx paired pretty well with the black niobium.
Niobium spike ends are pretty much non-existant, & these make a decent alternative. I did end up going back to the niobium ball ends, but having these available is cool.