Duravent has made a change after a decades long run of the popular Duratech Class-A chimney support "boxes" remaining the same, requiring an additional adaptor to go between the support and stovepipe below. 

They now all come with a built in "universal adaptor" that is used to connect to either single or double wall pipe between the ceiling support and stove. this change is only in the Duratech product line (DuraPlus still requires the additional adaptor).

(New support pictured on left, discontinued support pictured on right)