Interconnects: solid or hollow core wire?

I know what solid core is. I know what stranded is. I do not know what hollow core wire is? Isn't wire by definition solid as even stranded is made up of small solid core? Is there an audio cable that uses metal tubing?

Stranded is multiple stands of small guage wires to make up the core.

Hmmm, I thought Supra used hollow core wire but they just confirmed that the wires are wrapped around an hollow tube of PE. Their literature is vague about it. It seems to suggest they use hollow wire... a new one on me, too, hence the question!

A good compromise is bubble core. Electrons love a good bubble bath.

I'd like to hear from the electrons themselves, please, about whether they like a good bubble bath or not.