Spotted some of these recently.
Bead caps are a type of findings used in bead work. And it's is VERY cheap. Not usually the main item in a piece, as it is usually used to finish a piece. For example it is used in a necklace like this>
Because of the multiple strand, it has to have a cap to hold all the strands firmly.
Sorry, I can't find a picture at the back, where you can really see what I meant.
I've seen many accessories that use findings. Crimps, jump rings, wires. (p/s: Another post for another day)
Just let your creativity take over.