You just have to look at the photos when ordering the circular barbells. Different manufacturers will make them a bit different. On this website there is a big range of styles in different gauges and materials.

To get the wide opening on CBBs, I use a pair of needle nose pliers which I covered with electrical tape, so not to scratch the barbell.
What I do is place the closed pliers inside the CBB then open them until they touch the inside edges, checking the spacing between ball ends and pliers is even, this helps the bar bend evenly.
Then I slowly & gently open the pliers thus stretching the CBB open, much the same as can be done with CBRs when worn without the bead. I like the look of Stretched out CBBs and CBRs in my septum piercing

Thanks for info,I can do that.I'll just have to maybe get a little smaller and spread it to make my size.The ones I have got so far have had the balls too close for my likes.

Thanks for info !!

I do believe you're talking about curved barbells vs. circular

Circular:

Curved:

No,Not the curved barbell,The one i'm thinking about is similar to circular but looks more like a horse shoe.I think it may be old-school ?