Whether it represents the view through a telescope or the hydrogen atom, there is something elemental about this basic circular design.
Threadless ends will fit most of these posts
The Solid 14k Gold Circle threadless ends are available in solid ellow gold, rose gold, or white gold with a stainless steel threadless post.
The Sterling Silver Elemental threadless ends are available in solid un-plated silver, yellow gold plated sterling silver, or rose gold plated sterling silver with a stainless steel threadless post
The Circle end design measures approximately 6mm in diameter.
More threadless jewelry can be found here.