Not the white cowboy boots… but rather the metal ‘transition boot’ between the round ducts in the crawlspace and/or attic to the rectangular wall or ceiling heat registers in rooms… that wrapped with asbestos.
What is asbestos? It’s a mineral fiber that was added to a variety of products in the past to strengthen them and to provide heat insulation and fire resistance.
Is this a problem? Yes, only if the boots are damaged, rusted or deteriorating; and the asbestos becomes “friable” – where asbestos material can be crumbled, pulverized, or reduced to powder by hand.