https://www.titanbarrels.com/
Just read about these on Whiskey Wash, I think. They're interesting in that they'd, in theory, maintain the ratio of wood to spirits contact surface area of a full sized barrel, but in a smaller size with what looks like a sanitary fitting on top for taking samples. Might be a way to age smaller volumes for long periods without over-oaking them or also could be a way to cheaply try out different wood species and get creative with different barrel ends and inserts.
I assume they wouldn't count for TTB designations like "straight" or "bonded" or terms like that which rely on time spent in charred oak barrels.