Hello - the standard chimney is included when you purchase the range hood. It comes with (2) 16" standard chimney sleeves. It will work for standard 8-9 foot ceilings.
I found the chimney collar "crown molding" online at the range hood store. They are "on sale" for $39-49 with free shipping. Didn't pay attention to when the "sale" ended. Hope this helps.
ZLINE Kitchen and Bath
oggyd48
Richardson Construction LLC