It's 6" dia. single-wall uninsulated flexible aluminum ducting -- like
some I have seen for a drier (but bigger, of course). It was in the
ducting section of Menards, not in the dryer accessories section. It's
of a spiral (more accurately "helical," I guess) construction, with a
crinkled appearance where successive turns overlap. As displayed in the
store it was 4' or less long.
I did manage to ease it out to the required length (after throwing away
several inches from each end, where some of these successive turns
pulled apart) by bending -- not easy in the space between joists, floor
above, and suspended ceiling grid -- and pulling gently. I'm sure there
must be a more tedious and error-prone way, however -- in case I have to
do the same again.
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still be run from boardrooms in the USA and elsewhere, not by your
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